Blocked mercaptosilane coupling agents for filled rubbers

ABSTRACT

Disclosed herein is a rubber composition comprising:  
     a) a blocked mercaptosilane of a defined structure, wherein the blocking group contains an unsaturated heteroatom or carbon chemically bound directly to sulfur via a single bond and, optionally, may be substituted with one or more carboxylate ester or carboxylic acid functional groups;  
     b) an organic polymer; and  
     c) a filler.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a division of co-pending application Ser. No. 09/284,841,filed Apr. 21, 1999, which is a 371 of PCT/US98/17391, Aug. 21, 1998,which claims priority to U.S. Provisional Patent Application No.60/056,566, filed Aug. 21, 1997

FIELD OF THE INVENTION

[0002] This invention relates to sulfur silane coupling agents which arelatent, that is, they are in a state of reduced activity until such atime as one finds it useful to activate them. The invention also relatesto the manufacture of rubbers including inorganic fillers and thesesilane coupling agents, as well as to the manufacture of the silanes.

BACKGROUND

[0003] The majority of art in the use of sulfur-containing couplingagents in rubber involves silanes containing one or more of thefollowing chemical bond types: S—H (mercapto), S—S (disulfide orpolysulfide), or C═S (thiocarbonyl). Mercaptosilanes have offeredsuperior coupling at substantially reduced loadings; however, their highchemical reactivity with organic polymers leads to unacceptably highviscosities during processing and premature curing (scorch). Theirundesirability is aggravated by their odor. As a result, other, lessreactive coupling agents have been found. Hence, a compromise must befound between coupling and the associated final properties,processability, and required loading levels, which invariably leads tothe need to use substantially higher coupling agent loadings than wouldbe required with mercaptosilanes, and often also to the need to dealwith less than optimal processing conditions, both of which lead tohigher costs.

[0004] The prior art discloses acylthioalkyl silanes, such asCH₃C(═O)S(CH₂)₁₋₃Si(OR)₃ (M. G. Voronkov et al. in Inst. Org. Khim.,Irkutsk, Russia) and HOC(═O)CH₂CH₂C(═O)S(CH₂)₃Si(OC₂H₅)₃ (U.S. Pat. No.3,922,436 to R. Bell et al.). Takeshita and Sugawara disclosed inJapanese Patent JP 63270751 A2 the use of compounds represented by thegeneral formula CH2═C(CH₃)C(═O)S(CH₂)₁₋₆Si(OCH₃)₃ in tire treadcompositions; but these compounds are not desirable because theunsaturation α,β to the carbonyl group of the thioester has theundesirable potential to polymerize during the compounding process orduring storage.

[0005] Prior art by Yves Bomal and Olivier Durel in Australian PatentAU-A-10082/97 discloses the use in rubber of silanes of the structurerepresented by R¹ _(n)X_(3−n)Si—(Alk)_(m)(Ar)_(p)—S(C═O)—R where R¹ isphenyl or alkyl; X is halogen, alkoxy, cycloalkoxy, acyloxy, or OH; Alkis alkyl; Ar is aryl; R is alkyl, alkenyl, or aryl; n is 0 to 2; and mand p are each 0 or 1, but not both zero. This prior art, however,stipulates that compositions of the structures of Formula (1P) must beused in conjunction with functionalized siloxanes. In addition, theprior art does not disclose or suggest the use of compounds of Formula(1P) as latent mercaptosilane coupling agents, nor does it disclose orsuggest the use of these compounds in any way which would give rise tothe advantages of using them as a source of latent mercaptosilane.

[0006] U.S. Pat. No. 4,519,430 to Ahmad et al. and U.S. Pat. No.4,184,998 to Shippy et al. disclose the blocking of a mercaptosilanewith an isocyanate to form a solid which is added to a tire composition,which mercaptan reacts into the tire during heating, which could happenat any time during processing since this is a thermal mechanism. Thepurpose of this silane is to avoid the sulfur smell of themercaptosilane, not to improve the processing of the tire. Moreover, theisocyanate used has toxicity issues when used to make the silane andwhen released during rubber processing.

[0007] U.S. Pat. No. 3,957,718 to Porchet et al. discloses compositionscontaining silica, phenoplasts or aminoplasts, and silanes, such asxanthates, thioxanthates, and dithiocarbamates; however, the prior artdoes not disclose or suggest the use of these silanes as latentmercaptosilane coupling agents, nor does it suggest or disclose theadvantage of using them as a source of latent mercaptosilane. Thereremains a need for effective latent coupling agents which exhibit theadvantages of mercaptosilanes without exhibiting the disadvantages suchas described herein.

SUMMARY OF THE INVENTION

[0008] The silanes of the present invention are mercaptosilanederivatives in which the mercapto group is blocked (“blockedmercaptosilanes”), i.e., the mercapto hydrogen atom is replaced byanother group (hereafter referred to as “blocking group”). Specifically,the silanes of the present invention are blocked mercaptosilanes inwhich the blocking group contains an unsaturated heteroatom or carbonchemically bound directly to sulfur via a single bond. This blockinggroup optionally may be substituted with one or more carboxylate esteror carboxylic acid functional groups. The use of these silanes in themanufacture of inorganic filled rubbers is taught wherein they aredeblocked by the use of a deblocking agent during the manufacturingprocess. The manufacture of such silanes is taught as well.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Silane Structures

[0010] The blocked mercaptosilanes can be represented by the Formulae(1-2):

[[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G—(SiX₃)_(s)  (1);

[0011] and

[(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)

[0012] wherein

[0013] Y is a polyvalent species (Q)_(z)A(═E), preferably selected fromthe group consisting of —C(═NR)—; —SC(═NR)—; —SC(═O)—; (—NR)C(═O)—;(—NR)C(═S)—; —OC(═O)—; —OC(═S)—; —C(═O)—; —SC(═S)—; —C(═S)—; —S(═O)—;—S(═O)₂—; —OS(═O)₂—; (—NR)S(═O)₂—; —SS(═O)—; —OS(═O)—; (—NR)S(═O)—;—SS(═O)₂—; (—S)₂P(═O)—; —(—S)P(═O)—; —P(═O)(—)₂; (—S)₂P(═S)—;—(—S)P(═S)—; —P(═S)(—)₂; (—NR)₂P(═O)—; (—NR)(—S)P(═O)—; (—O)(—NR)P(—O)—;(—O)(—S)P(═O)—; (—O)₂P(═O)—; —(—O)P(═O)—; —(—NR)P(═O)—; (—NR)₂P(═S)—;(—NR)(—S)P(═S)—; (—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—;—(—O)P(═S)—; and —(—NR)P(═S)—; each wherein the atom (A) attached to theunsaturated heteroatom (E) is attached to the sulfur, which in turn islinked via a group G to the silicon atom;

[0014] each R is chosen independently from hydrogen, straight, cyclic,or branched alkyl that may or may not contain unsaturation, alkenylgroups, aryl groups, and aralkyl groups, with each R containing from 1to 18 carbon atoms;

[0015] each G is independently a monovalent or polyvalent group derivedby substitution of alkyl, alkenyl, aryl, or aralkyl wherein G cancontain from 1 to 18 carbon atoms, with the proviso that G is not suchthat the silane would contain an α,β-unsaturated carbonyl including acarbon-carbon double bond next to the thiocarbonyl group, and if Gdirectly bonded to Y is univalent (i.e., if p=0), G can be a hydrogenatom;

[0016] X is independently selected from the group consisting of —Cl,—Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO— or R₂N—, —R, —(OSiR₂)_(t)(OSiR₃)wherein each R and G is as above and at least one X is not —R;

[0017] Q is oxygen, sulfur, or (—NR—);

[0018] A is carbon, sulfur, phosphorus, or sulfonyl;

[0019] E is oxygen, sulfur, or NR;

[0020] p is 0 to 5; r is 1 to 3; z is 0 to 2; q is 0 to 6; a is 0 to 7;b is 1 to 3; j is 0 to 1, but it may be 0 only if p is 1; c is 1 to 6,preferably 1 to 4; t is 0 to 5; s is 1 to 3; k is 1 to 2; with theprovisos that (A) if A is carbon, sulfur, or sulfonyl, then (i) a+b=2and (ii) k=1; (B) if A is phosphorus, then a+b=3 unless both (i) c>1 and(ii) b=1, in which case a=c+1; and if A is phosphorus, then k is 2.

[0021] As used herein, “alkyl” includes straight, branched, and cyclicalkyl groups, and “alkenyl” includes straight, branched, and cyclicalkenyl groups containing one or more carbon-carbon double bonds.Specific alkyls include methyl, ethyl, propyl, isobutyl, and specificaralkyls include phenyl, tolyl, and phenethyl. As used herein, “cyclicalkyl” or “cyclic alkenyl” also includes bicyclic and higher cyclicstructures, as well as cyclic structures further substituted with alkylgroups. Representative examples include norbornyl, norbornenyl,ethylnorbornyl, ethylnorbornenyl, ethylcyclohexyl, ethylcyclohexenyl,and cyclohexylcyclohexyl.

[0022] Representative examples of the functional groups (—YS—) presentin the silanes of the present invention include thiocarboxylate ester,—C(═O)S— (any silane with this functional group is a “thiocarboxylateester silane”); dithiocarboxylate, —C(═S)S— (any silane with thisfunctional group is a “dithiocarboxylate ester silane”); thiocarbonateester, —O—C(═O)S— (any silane with this functional group is a“thiocarbonate ester silane”); dithiocarbonate ester, —S—C(═O)S— and—O—C(═S)S— (any silane with this functional groups is a “dithiocarbonateester silane”); trithiocarbonate ester, —S—C(═S)S— (any silane with thisfunctional group is a “trithiocarbonate ester silane”); dithiocarbamateester, (—N—)C(═S)S— (any silane with this functional group is a“dithiocarbamate ester silane”); thiosulfonate ester, —S(═O)₂S— (anysilane with this functional group is a “thiosulfonate ester silane”);thiosulfate ester, —O—S(═O)₂S— (any silane with this functional group isa “thiosulfate ester silane”); thiosulfamate ester, (—N—)S(═O)₂S— (anysilane with this functional group is a “thiosulfamate ester silane”);thiosulfinate ester, —S(═O)S— (any silane with this functional group isa “thiosulfinate ester silane”); thiosulfite ester, —O—S(═O)S— (anysilane with this functional group is a “thiosulfite ester silane”);thiosulfimate ester, (—N—)S(═O)—S— (any silane with this functionalgroup is a “thiosulfimate ester silane”); thiophosphate ester,P(═O)(O—)₂(S—) (any silane with this functional group is a“thiophosphate ester silane”); dithiophosphate ester, P(═O)(O—)(S—)₂ orP(═S)(O—)₂(S—) (any silane with this functional group is a“dithiophosphate ester silane”); trithiophosphate ester, P(═O)(S—)₃ orP(═S)(O—)(S—)₂ (any silane with this functional group is a“trithiophosphate ester silane”); tetrathiophosphate ester P(═S)(S—)₃(any silane with this functional group is a “tetrathiophosphate estersilane”); thiophosphamate ester, —P(═O)(—N—)(S—) (any silane with thisfunctional group is a “thiophosphamate ester silane”); dithiophosphamateester, —P(═S)(—N—)(S—) (any silane with this functional group is a“dithiophosphamate ester silane”); thiophosphoramidate ester,(—N—)P(═O)(O—)(S—) (any silane with this functional group is a“thiophosphoramidate ester silane”); dithiophosphoramidate ester,(—N—)P(═O)(S—)₂ or (—N—)P(═S)(O—)(S—) (any silane with this functionalgroup is a “dithiophosphoramidate ester silane”); trithiophosphoramidateester, (—N—)P(═S)(S—)₂ (any silane with this functional group is a“trithiophosphorarnidate ester silane”).

[0023] Novel silanes of the present invention are those wherein Y groupsare —C(═NR)—; —SC(═NR)—; —SC(═O)—; —OC(═O)—; —S(═O)—; —S(═O)₂—;—OS(═O)₂—; —(NR)S(═O)₂—; —SS(═O)—; —OS(═O)—; —(NR)S(═O)—; —SS(═O)₂—;(—S)₂P(═O)—; —(—S)P(═O)—; —P(═O)(—)₂; (—S)₂P(═S)—; —(—S)P(═S)—;—P(═S)(—)₂; (—NR)₂P(═O)—; (—NR)(—S)P(═O)—; (—O)(—NR)P(═O)—;(—O)(—S)P(═O)—; (—O)₂P(═O)—; —(—O)P(═O)—; —(—NR)P(═O)—; (—NR)₂P(═S)—;(—NR)(—S)P(═S)—; (—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—;—(—O)P(═S)—; and —(—NR)P(═S)—. Particularly preferred of these are—OC(═O)—; —SC(═O)—; —S(═O)—; —OS(═O)—; —(—S)P(═O)—; and —P(═O)(—)₂.

[0024] Another novel silane would be one wherein Y is —C(═O)— wherein Ghas a primary carbon attached to the carbonyl and is a C₂-C₂ alkyl, morepreferably a C₆-C₈ alkyl.

[0025] Another preferred novel structure is of the formX₃SiGSC(═O)GC(═O)SGSiX₃ wherein G is a divalent hydrocarbon.

[0026] Examples of G include —(CH₂)_(n)— wherein n is 1 to 12,diethylene cyclohexane, 1,2,4-triethylene cyclohexane, and diethylenebenzene. It is preferred that the sum of the carbon atoms within the Ggroups within the molecule are from 3 to 18, more preferably 6 to 14.This amount of carbon in the blocked mercaptosilane facilitates thedispersion of the inorganic filler into the organic polymers, therebyimproving the balance of properties in the cured filled rubber.

[0027] Preferable R groups are alkyls of C₁ to C₄ and H.

[0028] Specific examples of X are methoxy, ethoxy, isobutoxy, propoxy,isopropoxy, acetoxy, and oximato. Methoxy, acetoxy, and ethoxy arepreferred. At least one X must be reactive (i.e., hydrolyzable).

[0029] Preferred embodiments are wherein p is 0 to 2; X is RO— orRC(═O)O—; R is hydrogen, phenyl, isopropyl, cyclohexyl, or isobutyl; Gis a substituted phenyl or substituted straight chain alkyl of C₂ toC₁₂. The most preferred embodiments include those wherein p is zero, Xis ethoxy, and G is a C₃-C₁₂ alkyl derivative.

[0030] Representative examples of the silanes of the present inventioninclude:

[0031] 2-triethoxysilyl-1-ethyl thioacetate; 2-trimethoxysilyl-1-ethylthioacetate; 2-(methyldimethoxysilyl)-1-ethyl thioacetate;3-trimethoxysilyl-1-propyl thioacetate; triethoxysilylmethylthioacetate; trimethoxysilylmethyl thioacetate; triisopropoxysilylmethylthioacetate; methyldiethoxysilylmethyl thioacetate;methyldimethoxysilylmethyl thioacetate; methyldiisopropoxysilylmethylthioacetate; dimethylethoxysilylmethyl thioacetate;dimethylmethoxysilylmethyl thioacetate; dimethylisopropoxysilylmethylthioacetate; 2-triisopropoxysilyl-1-ethyl thioacetate;2-(methyldiethoxysilyl)-1-ethyl thioacetate;2-(methyldiisopropoxysilyl)-1-ethyl thioacetate;2-(dimethylethoxysilyl)-1-ethyl thioacetate;2-(dimethylmethoxysilyl)-1-ethyl thioacetate;2-(dimethylisopropoxysilyl)-1-ethyl thioacetate;3-triethoxysilyl-1-propyl thioacetate; 3-triisopropoxysilyl-1-propylthioacetate; 3-methyldiethoxysilyl-1-propyl thioacetate;3-methyldimethoxysilyl-1propyl thioacetate;3-methyldiisopropoxysilyl-1-propyl thioacetate;1-(2-triethoxysilyl-1-ethyl)-4-thioacetylcyclohexane;1-(2-triethoxysilyl-1-ethyl)-3-thioacetylcyclohexane;2-triethoxysilyl-5-thioacetylnorbornene;2-triethoxysilyl-4-thioacetylnorbornene;2-(2-triethoxysilyl-1-ethyl)-5-thioacetylnorbornene;2-(2-triethoxysilyl-1-ethyl)-4-thioacetylnorbornene;1-(1-oxo-2-thia-5-triethoxysilylpenyl)benzoic acid;6-triethoxysilyl-1-hexyl thioacetate; 1-triethoxysilyl-5-hexylthioacetate; 8-triethoxysilyl-1-octyl thioacetate;1-triethoxysilyl-7-octyl thioacetate; 6-triethoxysilyl-1-hexylthioacetate; 1-triethoxysilyl-5-octyl thioacetate;8-trimethoxysilyl-1-octyl thioacetate; 1-trimethoxysilyl-7-octylthioacetate; 10-triethoxysilyl-1-decyl thioacetate;1-triethoxysilyl-9-decyl thioacetate; 1-triethoxysilyl-2-butylthioacetate; 1-triethoxysilyl-3-butyl thioacetate;1-triethoxysilyl-3-methyl-2-butyl thioacetate;1-triethoxysilyl-3-methyl-3-butyl thioacetate;3-trimethoxysilyl-1-propyl thiooctanoate; 3-triethoxysilyl-1-propylthiopalmitate; 3-triethoxysilyl-1-propyl thiooctanoate;3-triethoxysilyl-1-propyl thiobenzoate; 3-triethoxysilyl-1-propylthio-2-ethylhexanoate; 3-methyldiacetoxysilyl-1-propyl thioacetate;3-triacetoxysilyl-1-propyl thioacetate; 2-methyldiacetoxysilyl-1-ethylthioacetate; 2-triacetoxysilyl-1-ethyl thioacetate;1-methyldiacetoxysilyl-1-ethyl thioacetate; 1-triacetoxysilyl-1-ethylthioacetate; tris-(3-triethoxysilyl-1-propyl)trithiophosphate;bis-(3-triethoxysilyl-1-propyl)methyldithiophosphonate;bis-(3-triethoxysilyl-1-propyl)ethyldithiophosphonate;3-triethoxysilyl-1-propyldimethylthiophosphinate;3-triethoxysilyl-1-propyldiethylthiophosphinate;tris-(3-triethoxysilyl-1-propyl)tetrathiophosphate;bis-(3-triethoxysilyl-1-propyl)methyltrithiophosphonate;bis-(3-triethoxysilyl-1-propyl)ethyltrithiophosphonate;3-triethoxysilyl-1propyldimethyldithiophosphinate;3-triethoxysilyl-1-propyldiethyldithiophosphinate;tris-(3-methyldimethoxysilyl-1-propyl)trithiophosphate;bis-(3-methyldimethoxysilyl-1-propyl)methyldithiophosphonate;bis-(3-methyldimethoxysilyl-1-propyl)ethyldithiophosphonate;3-methyldimethoxysilyl-1-propyldimethylthiophosphinate;3-methyldimethoxysilyl-1-propyldiethylthiophosphinate;3-triethoxysilyl-1-propylmethylthiosulphate;3-triethoxysilyl-1propylmethanethiosulphonate;3-triethoxysilyl-1-propylethanethiosulphonate;3-triethoxysilyl-1-propylbenzenethiosulphonate;3-triethoxysilyl-1-propyltoluenethiosulphonate;3-triethoxysilyl-1-propylnaphthalenethiosulphonate;3-triethoxysilyl-1-propylxylenethiosulphonate;triethoxysilylmethylmethylthiosulphate;triethoxysilylmethylmethanethiosulphonate;triethoxysilylmethylethanethiosulphonate;triethoxysilylmethylbenzenethiosulphonate;triethoxysilylmethyltoluenethiosulphonate;triethoxysilylmethylnaphthalenethiosulphonate; andtriethoxysilylmethylxylenethiosulphonate.

[0032] Mixtures of various blocked mercaptosilanes may be used,including wherein synthetic methods result in a distribution of varioussilanes or where mixes of blocked mercaptosilanes are used for theirvarious blocking or leaving functionalities. Moreover, it is understoodthat the partial hydrolyzates of these blocked mercaptosilanes (i.e.,blocked mercaptosiloxanes) may also be encompassed by the blockedmercaptosilanes herein, in that these partial hydrolyzates will be aside product of most methods of manufacture of the blockedmercaptosilane or can occur upon storage of the blocked mercaptosilane,especially in humid conditions.

[0033] The silane, if liquid, may be loaded on a carrier, such as aporous polymer, carbon black, or silica so that it is in solid form fordelivery to the rubber. In a preferred mode, the carrier would be partof the inorganic filler to be used in the rubber.

[0034] Manufacture of Silanes

[0035] The methods of preparation for blocked mercaptosilanes caninvolve esterification of sulfur in a sulfur-containing silane anddirect incorporation of the thioester group into a silane, either bysubstitution of an appropriate leaving group or by addition across acarbon-carbon double bond. Illustrative examples of synthetic proceduresfor the preparation of thioester silanes would include: Reaction 1) thereaction between a mercaptosilane and an acid anhydride corresponding tothe thioester group present in the desired product; Reaction 2) reactionof an alkali metal salt of a mercaptosilane with the appropriate acidanhydride or acid halide; Reaction 3) the transesterification between amercaptosilane and an ester, optionally using any appropriate catalystsuch as an acid, base, tin compound, titanium compound, transition metalsalt, or a salt of the acid corresponding to the ester; Reaction 4) thetransesterification between a thioester silane and another ester,optionally using any appropriate catalyst such as an acid, base, tincompound, titanium compound, transition metal salt, or a salt of theacid corresponding to the ester; Reaction 5) the transesterificationbetween a 1-sila-2-thiacyclopentane or a 1-sila-2-thiacyclohexane and anester, optionally using any appropriate catalyst such as an acid, base,tin compound, titanium compound, transition metal salt, or a salt of theacid corresponding to the ester; Reaction 6) the free radical additionof a thioacid across a carbon-carbon double bond of an alkene-functionalsilane, catalyzed by UV light, heat, or the appropriate free radicalinitiator wherein, if the thioacid is a thiocarboxylic acid, the tworeagents are brought into contact with each other in such a way as toensure that whichever reagent is added to the other is reactedsubstantially before the addition proceeds; and Reaction 7) the reactionbetween an alkali metal salt of a thioacid with a haloalkylsilane.

[0036] Acid halides include but are not limited to, in addition toorganic acid halides, inorganic acid halides, such as POT₃, SOT₂, SO₂T₂,COT₂, CST₂, PST₃ and PT₃, wherein T is a halide. Acid anhydrides includebut are not limited to, in addition to organic acid anhydrides (andtheir sulfur analogs), inorganic acid anhydrides such as SO₃, SO₂, P₂O₅,P₂S₅, H₂S₂O₇, CO₂, COS, and CS₂.

[0037] Illustrative examples of synthetic procedures for the preparationof thiocarboxylate-functional silanes would include: Reaction 8) thereaction between a mercaptosilane and a carboxylic acid anhydridecorresponding to the thiocarboxylate group present in the desiredproduct; Reaction 9) reaction of an alkali metal salt of amercaptosilane with the appropriate carboxylic acid anhydride or acidhalide; Reaction 10) the transesterification between a mercaptosilaneand a carboxylate ester, optionally using any appropriate catalyst, suchas an acid, base, tin compound, titanium compound, transition metalsalt, or a salt of the acid corresponding to the carboxylate ester;Reaction 11) the transesterification between athiocarboxylate-functional silane and another ester, optionally usingany appropriate catalyst, such as an acid, base, tin compound, titaniumcompound, transition metal salt, or a salt of the acid corresponding tothe other ester; Reaction 12) the transesterification between a1-sila-2-thiacyclopentane or a 1-sila-2-thiacyclohexane and acarboxylate ester, optionally using any appropriate catalyst, such as anacid, base, tin compound, titanium compound, transition metal salt, or asalt of the acid corresponding to the carboxylate ester; Reaction 13)the free radical addition of a thiocarboxylic acid across acarbon-carbon double bond of an alkene-functional silane, catalyzed byUV light, heat, or the appropriate free radical initiator; and Reaction14) the reaction between an alkali metal salt of a thiocarboxylic acidwith a haloalkylsilane.

[0038] Reactions 1 and 8 can be carried out by distilling a mixture ofthe mercaptosilane and the acid anhydride and optionally a solvent.Appropriate boiling temperatures of the mixture are in the range of 60°to 200° C.; preferably 70° to 170° C.; optionally 50° to 250° C. Thisprocess leads to a chemical reaction in which the mercapto group of themercaptosilane is esterified to the thioester silane analog with releaseof an equivalent of the corresponding acid. The acid typically is morevolatile than the acid anhydride. The reaction is driven by the removalof the more volatile acid by distillation. For the more volatile acidanhydrides, such as acetic anhydride, the distillation preferably iscarried out at ambient pressure to reach temperatures sufficient todrive the reaction toward completion. For less volatile materials,solvents such as toluene, xylene, glyme, and diglyme could be used withthe process to limit temperature. Alternatively, the process could berun at reduced pressure. It would be useful to use up to a twofoldexcess or more of the acid anhydride which would be distilled out of themixture after all of the more volatile reaction coproducts, consistingof acids and nonsilane esters, have been distilled out. This excess ofacid anhydride would serve to drive the reaction to completion, as wellas to help drive the coproducts out of the reaction mixture. At thecompletion of the reaction, distillation should be continued to driveout the remaining acid anhydride. The product optionally could bedistilled.

[0039] Reactions 2 and 9 can be carried out in two steps. The first stepwould involve conversion of the mercaptosilane to a corresponding metalderivative. Alkali metal derivatives, especially sodium or alsopotassium and lithium, are preferable. The metal derivative would beprepared by adding the alkali metal or a strong base derived from thealkali metal to the mercaptosilane. The reaction would occur at ambienttemperature. Appropriate bases would include alkali metal alkoxides,amides, hydrides, and mercaptides. Alkali metal organometallic reagentswould also be effective. Grignard reagents would yield magnesiumderivatives, which would be another alternative. Solvents, such astoluene, xylene, benzene, aliphatic hydrocarbons, ethers, and alcoholscould be used to prepare the alkali metal derivatives. Once the alkalimetal derivative is prepared, any alcohol present would need to beremoved. This could be done by distillation or evaporation. Alcohols,such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol,and t-butanol may be removed by azeotropic distillation with benzene,toluene, xylene, or aliphatic hydrocarbons. Toluene and xylene arepreferable; toluene is most preferable. The second step in the overallprocess would be to add to this solution, with stirring, the acidchloride or acid anhydride at temperatures between −20° C. and theboiling point of the mixture, preferably at temperatures between 0° C.and ambient temperature. The product would be isolated by removing thesalt and solvent. It could be purified by distillation.

[0040] Reactions 3 and 10 could be carried out by distilling a mixtureof the mercaptosilane and the ester and optionally a solvent and/or acatalyst. Appropriate boiling temperatures of the mixture would be above100° C. This process leads to a chemical reaction in which the mercaptogroup of the mercaptosilane is esterified to the thioester silane analogwith release of an equivalent of the corresponding alcohol. The reactionis driven by the removal of the alcohol by distillation, either as themore volatile species, or as an azeotrope with the ester. For the morevolatile esters the distillation is suitably carried out at ambientpressure to reach temperatures sufficient to drive the reaction towardcompletion. For less volatile esters, solvents, such as toluene, xylene,glyme, and diglyme could be used with the process to limit temperature.Alternatively, the process could be run at reduced pressure. It isuseful to use up to a twofold excess or more of the ester, which wouldbe distilled out of the mixture after all of the alcohol coproduct hasbeen distilled out. This excess ester would serve to drive the reactionto completion as well as to help drive the coproduct alcohol out of thereaction mixture. At the completion of the reaction, distillation wouldbe continued to drive out the remaining ester. The product optionallycould be distilled.

[0041] Reactions 4 and 11 could be carried out by distilling a mixtureof the thioester silane and the other ester and optionally a solventand/or a catalyst. Appropriate boiling temperatures of the mixture wouldbe above 80° C.; preferably above 100° C. The temperature wouldpreferably not exceed 250° C. This process leads to a chemical reactionin which the thioester group of the thioester silane is transesterifiedto a new thioester silane with release of an equivalent of a new ester.The new thioester silane generally would be the least volatile speciespresent; however, the new ester would be more volatile than the otherreactants. The reaction would be driven by the removal of the new esterby distillation. The distillation can be carried out at ambient pressureto reach temperatures sufficient to drive the reaction towardcompletion. For systems containing only less volatile materials,solvents, such as toluene, xylene, glyme, and diglyme could be used withthe process to limit temperature. Alternatively, the process could berun at reduced pressure. It would be useful to use up to a twofoldexcess or more of the other ester, which would be distilled out of themixture after all of the new ester coproduct has been distilled out.This excess other ester would serve to drive the reaction to completionas well as to help drive the coproduct other ester out of the reactionmixture. At the completion of the reaction, distillation would becontinued to drive out the remaining said new ester. The productoptionally then could be distilled.

[0042] Reactions 5 and 12 could be carried out by heating a mixture ofthe 1-sila-2-thiacyclopentane or the 1-sila-2-thiacyclohexane and theester with the catalyst. Optionally, the mixture could be heated orrefluxed with a solvent, preferably a solvent whose boiling pointmatches the desired temperature. Optionally a solvent of higher boilingpoint than the desired reaction temperature can be used at reducedpressure, the pressure being adjusted to bring the boiling point down tothe desired reaction temperature. The temperature of the mixture wouldbe in the range of 80° to 250° C.; preferably 100° to 200° C. Solvents,such as toluene, xylene, aliphatic hydrocarbons, and diglyme could beused with the process to adjust the temperature. Alternatively, theprocess could be run under reflux at reduced pressure. The mostpreferable condition is to heat a mixture of the1-sila-2-thiacyclopentane or the 1-sila-2-thiacyclohexane and the ester,without solvent, preferably under inert atmosphere, for a period of 20to 100 hours at a temperature of 120° to 170° C. using the sodium,potassium, or lithium salt of the acid corresponding to the ester as acatalyst. The process leads to a chemical reaction in which thesulfur-silicon bond of the 1-sila-2-thiacyclopentane or the1-sila-2-thiacyclohexane is transesterified by addition of the esteracross said sulfur-silicon bond. The product is the thioester silaneanalog of the original 1-sila-2-thiacyclopentane or the1-sila-2-thiacyclohexane. Optionally, up to a twofold excess or more ofthe ester would be used to drive the reaction toward completion. At thecompletion of the reaction, the excess ester can be removed bydistillation. The product optionally could be purified by distillation.

[0043] Reactions 6 and 13 can be carried out by heating or refluxing amixture of the alkene-functional silane and the thioacid. Aspects ofReaction 13 have been disclosed previously in U.S. Pat. No. 3,692,812and by G. A. Gornowicz et al., in J. Org. Chem. (1968), 33(7), 2918-24.The uncatalyzed reaction can occur at temperatures as low as 105° C.,but often fails. The probability of success increases with temperatureand becomes high when the temperature exceeds 160° C. The reaction maybe made reliable and the reaction brought largely to completion by usingUV radiation or a catalyst. With a catalyst, the reaction can be made tooccur at temperatures below 90° C. Appropriate catalysts are freeradical initiators, e.g., peroxides, preferably organic peroxides, andazo compounds. Examples of peroxide initiators include peracids, such asperbenzoic and peracetic acids; esters of peracids; hydroperoxides, suchas t-butyl hydroperoxide; peroxides, such as di-t-butyl peroxide; andperoxy-acetals and ketals, such as 1,1-bis(t-butylperoxy)cyclohexane, orany other peroxide. Examples of azo initiators includeazobisisobutyronitrile (AIBN), 1,1-azobis(cyclohexanecarbonitrile)(VAZO, DuPont product); and azo-tert-butane, The reaction can be run byheating a mixture of the alkene-functional silane and the thioacid withthe catalyst. It is preferable for the overall reaction to be run on anequimolar or near equimolar basis to get the highest conversions. Thereaction is sufficiently exothermic that it tends to lead to a rapidtemperature increase to reflux followed by a vigorous reflux as thereaction initiates and continues rapidly. This vigorous reaction canlead to hazardous boil-overs for larger quantities. Side reactions,contamination, and loss in yield can result as well from uncontrolledreactions. The reaction can be controlled effectively by adding partialquantities of one reagent to the reaction mixture, initiating thereaction with the catalyst, allowing the reaction to run its courselargely to completion, and then adding the remains of the reagent,either as a single addition or as multiple additives. The initialconcentrations and rate of addition and number of subsequent additionsof the deficient reagent depend on the type and amount of catalyst used,the scale of the reaction, the nature of the starting materials, and theability of the apparatus to absorb and dissipate heat. A second way ofcontrolling the reaction would involve the continuous addition of onereagent to the other with concomitant continuous addition of catalyst.Whether continuous or sequential addition is used, the catalyst can beadded alone and/or preblended with one or both reagents or combinationsthereof Two methods are preferred for reactions involving thiolaceticacid and alkene-functional silanes containing terminal carbon-carbondouble bonds. The first involves initially bringing thealkene-functional silane to a temperature of 160° to 180° C., or toreflux, whichever temperature is lower. The first portion of thiolaceticacid is added at a rate as to maintain up to a vigorous, but controlled,reflux. For alkene-functional silanes with boiling points above 100° to120° C., this reflux results largely from the relatively low boilingpoint of thiolacetic acid (88° to 92° C., depending on purity) relativeto the temperature of the alkene-functional silane. At the completion ofthe addition, the reflux rate rapidly subsides. It often acceleratesagain within several minutes, especially if an alkene-functional silanewith a boiling point above 120° C. is used, as the reaction initiates.If it does not initiate within 10 to 15 minutes, initiation can bebrought about by addition of catalyst. The preferred catalyst isdi-t-butyl peroxide. The appropriate quantity of catalyst is from 0.2 to2 percent, preferably from 0.5 to 1 percent, of the total mass ofmixture to which the catalyst is added. The reaction typically initiateswithin a few minutes as evidenced by an increase in reflux rate. Thereflux temperature gradually increases as the reaction proceeds. Thenthe next portion of thiolacetic acid is added, and the aforementionedsequence of steps is repeated. The preferred number of thiolaceticadditions for total reaction quantities of about one to about fourkilograms is two, with about one-third of the total thiolacetic acidused in the first addition and the remainder in the second. For totalquantities in the range of about four to ten kilograms, a total of threethiolacetic additions is preferred, the distribution being approximately20 percent of the total used in the first addition, approximately 30percent in the second addition, and the remainder in the third addition.For larger scales involving thiolacetic acid and alkene-functionalsilanes, it is preferable to use more than a total of three thiolaceticadditions and, more preferably, to add the reagents in the reverseorder. Initially, the total quantity of thiolacetic acid is brought toreflux. This is followed by continuous addition of the alkene-functionalsilane to the thiolacetic acid at such a rate as to bring about a smoothbut vigorous reaction rate. The catalyst, preferably di-t-butylperoxide,can be added in small portions during the course of the reaction or as acontinuous flow. It is best to accelerate the rate of catalyst additionas the reaction proceeds to completion to obtain the highest yields ofproduct for the lowest amount of catalyst required. The total quantityof catalyst used should be 0.5 to 2 percent of the total mass ofreagents used. Whichever method is used, the reaction is followed up bya vacuum stripping process to remove volatiles and unreacted thiolaceticacid and silane. The product may be purified by distillation.

[0044] Methods to run Reactions 7 and 14 can be carried out in twosteps. The first step involves preparation of a salt of the thioacid.Alkali metal derivatives are preferred, with the sodium derivative beingmost preferred. These salts would be prepared as solutions in solventsin which the salt is appreciably soluble, but suspensions of the saltsas solids in solvents in which the salts are only slightly soluble arealso a viable option. Alcohols, such as propanol, isopropanol, butanol,isobutanol, and t-butanol, and preferably methanol and ethanol areuseful because the alkali metal salts are slightly soluble in them. Incases where the desired product is an alkoxysilane, it is preferable touse an alcohol corresponding to the silane alkoxy group to preventtransesterification at the silicon ester. Alternatively, nonproticsolvents can be used. Examples of appropriate solvents are ethers orpolyethers such as glyme, diglyme, and dioxanes; N,N-dimethylformamide;N,N-dimethylacetamide; dimethylsulfoxide; N-methylpyrrolidinone; orhexamethylphosphoramide. Once a solution, suspension, or combinationthereof of the salt of the thioacid has been prepared, the second stepis to react it with the appropriate haloalkylsilane. This may beaccomplished by stirring a mixture of the haloalkylsilane with thesolution, suspension, or combination thereof of the salt of the thioacidat temperatures corresponding to the liquid range of the solvent for aperiod of time sufficient to complete substantially the reaction.Preferable temperatures are those at which the salt is appreciablysoluble in the solvent and at which the reaction proceeds at anacceptable rate without excessive side reactions. With reactionsstarting from chloroalkylsilanes in which the At chlorine atom is notallylic or benzylic, preferable temperatures are in the range of 60° to160° C. Reaction times can range from one or several hours to severaldays. For alcohol solvents where the alcohol contains four carbon atomsor fewer, the most preferred temperature is at or near reflux. Whendiglyme is used as a solvent, the most preferred temperature is in therange of 70° to 120° C., depending on the thioacid salt used. If thehaloalkylsilane is a bromoalkylsilane or a chloroalkylsilane in whichthe chlorine atom is allylic or benzylic, temperature reductions of 30°to 60° C. are appropriate relative to those appropriate for nonbenzylicor nonallylic chloroalkylsilanes because of the greater reactivity ofthe bromo group. Bromoalkylsilanes are preferred over chloroalkylsilanesbecause of their greater reactivity, lower temperatures required, andgreater ease in filtration or centrifugation of the coproduct alkalimetal halide. This preference, however, can be overridden by the lowercost of the chloroalkylsilanes, especially for those containing thehalogen in the allylic or benzylic position. For reactions betweenstraight chain chloroalkylethoxysilanes and sodium thiocarboxylates toform thiocarboxylate ester ethoxysilanes, it is preferable to useethanol at reflux for 10 to 20 hours if 5 to 20 percent mercaptosilaneis acceptable in the product. Otherwise, diglyme would be an excellentchoice, in which the reaction would be run preferably in the range of80° to 120° C. for one to three hours. Upon completion of the reactionthe salts and solvent should be removed, and the product may bedistilled to achieve higher purity.

[0045] If the salt of the thioacid to be used in Reactions 7 and 14 isnot commercially available, its preparation may be accomplished by oneof two methods, described below as Method A and Method B. Method Ainvolves adding the alkali metal or a base derived from the alkali metalto the thioacid. The reaction occurs at ambient temperature. Appropriatebases include alkali metal alkoxides, hydrides, carbonates, andbicarbonates. Solvents, such as toluene, xylene, benzene, aliphatichydrocarbons, ethers, and alcohols may be used to prepare the alkalimetal derivatives. In Method B, acid chlorides or acid anhydrides wouldbe converted directly to the salt of the thioacid by reaction with thealkali metal sulfide or hydrosulfide. Hydrated or partially hydrousalkali metal sulfides or hydrosulfides are available; however, anhydrousor nearly anhydrous alkali metal sulfides or hydrosulfides arepreferred. Hydrous materials can be used, however, but with loss inyield and hydrogen sulfide formation as a coproduct. The reactioninvolves addition of the acid chloride or acid anhydride to the solutionor suspension of the alkali metal sulfide and/or hydrosulfide andheating at temperatures ranging from ambient to the reflux temperatureof the solvent for a period of time sufficient largely to complete thereaction, as evidenced by the formation of the coproduct salts.

[0046] If the alkali metal salt of the thioacid is prepared in such away that an alcohol is present, either because it was used as a solvent,or because it formed, as for example, by the reaction of a thioacid withan alkali metal alkoxide, it may be desirable to remove the alcohol if aproduct low in mercaptosilane is desired. In this case, it would benecessary to remove the alcohol prior to reaction of the salt of thethioacid with the haloalkylsilane. This could be done by distillation orevaporation. Alcohols, such as methanol, ethanol, propanol, isopropanol,butanol, isobutanol, and t-butanol are preferably removed by azeotropicdistillation with benzene, toluene, xylene, or aliphatic hydrocarbons.Toluene and xylene are preferred.

[0047] Utility

[0048] The blocked mercaptosilanes described herein are useful ascoupling agents for organic polymers (i.e., rubbers) and inorganicfillers. The blocked mercaptosilanes are unique in that the highefficiency of the mercapto group can be utilized without the detrimentalside effects typically associated with the use of mercaptosilanes, suchas high processing viscosity, less than desirable filler dispersion,premature curing (scorch), and odor. These benefits are accomplishedbecause the mercaptan group initially is nonreactive because of theblocking group. The blocking group substantially prevents the silanefrom coupling to the organic polymer during the compounding of therubber. Generally, only the reaction of the silane —SiX₃ group with thefiller can occur at this stage of the compounding process. Thus,substantial coupling of the filler to the polymer is precluded duringmixing, thereby minimizing the undesirable premature curing (scorch) andthe associated undesirable increase in viscosity. One can achieve bettercured filled rubber properties, such as a balance of high modulus andabrasion resistance, because of the avoidance of premature curing.

[0049] In use, one or more of the blocked mercaptosilanes are mixed withthe organic polymer before, during, or after the compounding of thefiller into the organic polymer. It is preferred to add the silanesbefore or during the compounding of the filler into the organic polymer,because these silanes facilitate and improve the dispersion of thefiller. The total amount of silane present in the resulting combinationshould be about 0.05 to about 25 parts by weight per hundred parts byweight of organic polymer (phr), more preferably 1 to 10 phr. Fillerscan be used in quantities ranging from about 5 to 100 phr, morepreferably from 25 to 80 phr.

[0050] When reaction of the mixture to couple the filler to the polymeris desired, a deblocking agent is added to the mixture to deblock theblocked mercaptosilane. The deblocking agent may be added at quantitiesranging from about 0.1 to about 5 phr, more preferably in the range offrom 0.5 to 3 phr. If alcohol or water is present (as is common) in themixture, a catalyst (e.g., tertiary amines, Lewis acids, or thiols) maybe used to initiate and promote the loss of the blocking group byhydrolysis or alcoholysis to liberate the corresponding mercaptosilane.Alternatively, the deblocking agent may be a nucleophile containing ahydrogen atom sufficiently labile such that the hydrogen atom could betransferred to the site of the original blocking group to form themercaptosilane. Thus, with a blocking group acceptor molecule, anexchange of hydrogen from the nucleophile would occur with the blockinggroup of the blocked mercaptosilane to form the mercaptosilane and thecorresponding derivative of the nucleophile containing the originalblocking group. This transfer of the blocking group from the silane tothe nucleophile could be driven, for example, by a greater thermodynamicstability of the products (mercaptosilane and nucleophile containing theblocking group) relative to the initial reactants (blockedmercaptosilane and nucleophile). For example, if the nucleophile were anamine containing an N—H bond, transfer of the blocking group from theblocked mercaptosilane would yield the mercaptosilane and one of severalclasses of amides corresponding to the type of blocking group used. Forexample, carboxyl blocking groups deblocked by amines would yieldamides, sulfonyl blocking groups deblocked by amines would yieldsulfonamides, sulfinyl blocking groups deblocked by amines would yieldsulfinamides, phosphonyl blocking groups deblocked by amines would yieldphosphonamides, phosphinyl blocking groups deblocked by amines wouldyield phosphinamides. What is important is that regardless of theblocking group initially present on the blocked mercaptosilane andregardless of the deblocking agent used, the initially substantiallyinactive (from the standpoint of coupling to the organic polymer)blocked mercaptosilane is substantially converted at the desired pointin the rubber compounding procedure to the active mercaptosilane. It isnoted that partial amounts of the nucleophile may be used (i.e., astoichiometric deficiency), if one were to deblock only part of theblocked mercaptosilane to control the degree of vulcanization of aspecific formulation.

[0051] Water typically is present on the inorganic filler as a hydrate,or bound to a filler in the form of a hydroxyl group. The deblockingagent could be added in the curative package or, alternatively, at anyother stage in the compounding process as a single component. Examplesof nucleophiles would include any primary or secondary amines, or aminescontaining C═N double bonds, such as imines or guanidines, with theproviso that said amine contains at least one N—H (nitrogen-hydrogen)bond. Numerous specific examples of guanidines, amines, and imines wellknown in the art, which are useful as components in curatives forrubber, are cited in J. Van Alphen, Rubber Chemicals, (Plastics andRubber Research Institute TNO, Delft, Holland, 1973). Some examplesinclude N,N′-diphenylguanidine, N,N′,N″-triphenylguanidine,N,N′-di-ortho-tolylguanidine, orthobiguanide, hexamethylenetetramine,cyclohexylethylamine, dibutylamine, and 4,4′-diaminodiphenylmethane. Anygeneral acid catalysts used to transesterify esters, such as Bronsted orLewis acids, could be used as catalysts.

[0052] The rubber composition need not be, but preferably is,essentially free of functionalized siloxanes, especially those of thetype disclosed in Australian Patent AU-A-10082/97, which is incorporatedherein by reference. Most preferably, the rubber composition is free offunctionalized siloxanes.

[0053] In practice, sulfur vulcanized rubber products typically areprepared by thermomechanically mixing rubber and various ingredients ina sequentially stepwise manner followed by shaping and curing thecompounded rubber to form a vulcanized product. First, for the aforesaidmixing of the rubber and various ingredients, typically exclusive ofsulfur and sulfur vulcanization accelerators (collectively “curingagents”), the rubber(s) and various rubber compounding ingredientstypically are blended in at least one, and often (in the case of silicafilled low rolling resistance tires) two, preparatory thermomechanicalmixing stage(s) in suitable mixers. Such preparatory mixing is referredto as nonproductive mixing or nonproductive mixing steps or stages. Suchpreparatory mixing usually is conducted at temperatures up to 140° to200° C. and often up to 150° to 180° C. Subsequent to such preparatorymix stages, in a final mixing stage, sometimes referred to as aproductive mix stage, deblocking agent (in the case of this invention),curing agents, and possibly one or more additional ingredients are mixedwith the rubber compound or composition, typically at a temperature in arange of 50° to 130° C., which is a lower temperature than thetemperatures utilized in the preparatory mix stages to prevent or retardpremature curing of the sulfur curable rubber, which is sometimesreferred to as scorching of the rubber composition. The rubber mixture,sometimes referred to as a rubber compound or composition, typically isallowed to cool, sometimes after or during a process intermediate millmixing, between the aforesaid various mixing steps, for example, to atemperature of about 50° C. or lower. When it is desired to mold and tocure the rubber, the rubber is placed into the appropriate mold at aboutat least 130° C. and up to about 200° C., which will cause thevulcanization of the rubber by the mercapto groups on the mercaptosilaneand any other free sulfur sources in the rubber mixture.

[0054] By thermomechanical mixing, it is meant that the rubber compound,or composition of rubber and rubber compounding ingredients, is mixed ina rubber mixture under high shear conditions where it autogenously heatsup as a result of the mixing primarily due to shear and associatedfriction within the rubber mixture in the rubber mixer. Several chemicalreactions may occur at various steps in the mixing and curing processes.

[0055] The first reaction is a relatively fast reaction and isconsidered herein to take place between the filler and the SiX₃ group ofthe blocked mercaptosilane. Such reaction may occur at a relatively lowtemperature such as, for example, at about 120° C. The second and thirdreactions are considered herein to be the deblocking of themercaptosilane and the reaction which takes place between the sulfuricpart of the organosilane (after deblocking), and the sulfur vulcanizablerubber at a higher temperature, for example, above about 140° C.

[0056] Another sulfur source may be used, for example, in the form ofelemental sulfur as S₈. A sulfur donor is considered herein as a sulfurcontaining compound which liberates free, or elemental, sulfur at atemperature in a range of 140° to 190° C. Examples of such sulfur donorsmay be, but are not limited to, polysulfide vulcanization acceleratorsand organosilane polysulfides with at least two connecting sulfur atomsin its polysulfide bridge. The amount of free sulfur source addition tothe mixture can be controlled or manipulated as a matter of choicerelatively independently from the addition of the aforesaid blockedmercaptosilane. Thus, for example, the independent addition of a sulfursource may be manipulated by the amount of addition thereof and bysequence of addition relative to addition of other ingredients to therubber mixture.

[0057] Addition of an alkyl silane to the coupling agent system (blockedmercaptosilane plus additional free sulfur source and/or vulcanizationaccelerator) typically in a mole ratio of alkyl silane to blockedmercaptosilane in a range of 1/50 to 1/2 promotes an even better controlof rubber composition processing and aging.

[0058] A rubber composition is prepared by a process which comprises thesequential steps of:

[0059] (A) thermomechanically mixing, in at least one preparatory mixingstep, to a temperature of 140° to 200° C., alternatively to 140° to 190°C., for a total mixing time of 2 to 20 minutes, alternatively 4 to 15minutes, for such mixing step(s);

[0060] (i) 100 parts by weight of at least one sulfur vulcanizablerubber selected from conjugated diene homopolymers and copolymers, andcopolymers of at least one conjugated diene and aromatic vinyl compound,

[0061] (ii) 5 to 100 phr (parts per hundred rubber), preferably 25 to 80phr, of particulate filler, wherein preferably the filler contains 1 to85 weight percent carbon black,

[0062] (iii) 0.05 to 20 parts by weight filler of at least one blockedmercaptosilane;

[0063] (B) subsequently blending therewith, in a final thermomechanicalmixing step at a temperature to 50° to 130° C. for a time sufficient toblend the rubber, preferably between 1 to 30 minutes, more preferably 1to 3 minutes, at least one deblocking agent at about 0.05 to 20 parts byweight of the filler and a curing agent at 0 to 5 phr; and optionally

[0064] (C) curing said mixture at a temperature of 130° to 200° C. forabout 5 to 60 minutes.

[0065] The process may also comprise the additional steps of preparingan assembly of a tire or sulfur vulcanizable rubber with a treadcomprised of the rubber composition prepared according to this inventionand vulcanizing the assembly at a temperature in a range of 130° to 200°C.

[0066] Suitable organic polymers and fillers are well known in the artand are described in numerous texts, of which two examples include TheVanderbilt Rubber Handbook, R. F. Ohm, ed. (R. T. Vanderbilt Company,Inc., Norwalk, Conn., 1990), and Manual for the Rubber Industry, T.Kempermann, S. Koch, and J. Sumner, eds. (Bayer AG, Leverkusen, Germany,1993). Representative examples of suitable polymers include solutionstyrene-butadiene rubber (sSBR), styrene-butadiene rubber (SBR), naturalrubber (NR), polybutadiene (BR), ethylene-propylene co- and ter-polymers(EP, EPDM), and acrylonitrile-butadiene rubber (NBR). The rubbercomposition is comprised of at least one diene-based elastomer, orrubber. Suitable conjugated dienes are isoprene and 1,3-butadiene andsuitable vinyl aromatic compounds are styrene and alpha methyl styrene.Thus, the rubber is a sulfur curable rubber. Such diene based elastomer,or rubber, may be selected, for example, from at least one ofcis-1,4-polyisoprene rubber (natural and/or synthetic, and preferablynatural rubber), emulsion polymerization prepared styrene/butadienecopolymer rubber, organic solution polymerization preparedstyrene/butadiene rubber, 3,4-polyisoprene rubber, isoprene/butadienerubber, styrene/isoprene/butadiene terpolymer rubber,cis-1,4-polybutadiene, medium vinyl polybutadiene rubber (35 percent to50 percent vinyl), high vinyl polybutadiene rubber (50 percent to 75percent vinyl), styrene/isoprene copolymers, emulsion polymerizationprepared styrene/butadiene/acrylonitrile terpolymer rubber andbutadiene/acrylonitrile copolymer rubber. An emulsion polymerizationderived styrene/butadiene (eSBR) might be used having a relativelyconventional styrene content of 20 percent to 28 percent bound styreneor, for some applications, an eSBR having a medium to relatively highbound styrene content, namely, a bound styrene content of 30 percent to45 percent. Emulsion polymerization preparedstyrene/butadiene/acrylonitrile terpolymer rubbers containing 2 to 40weight percent bound acrylonitrile in the terpolymer are alsocontemplated as diene based rubbers for use in this invention.

[0067] The solution polymerization prepared SBR (sSBR) typically has abound styrene content in a range of 5 to 50 percent, preferably 9 to 36percent. Polybutadiene elastomer may be conveniently characterized, forexample, by having at least a 90 weight percent cis-1,4-content.

[0068] Representative examples of suitable filler materials includemetal oxides, such as silica (pyrogenic and precipitated), titaniumdioxide, aluminosilicate and alumina, siliceous materials includingclays and talc, and carbon black. Particulate, precipitated silica isalso sometimes used for such purpose, particularly when the silica isused in connection with a silane. In some cases, a combination of silicaand carbon black is utilized for reinforcing fillers for various rubberproducts, including treads for tires. Alumina can be used either aloneor in combination with silica. The term “alumina” can be describedherein as aluminum oxide, or Al₂O₃. The fillers may be hydrated or inanhydrous form. Use of alumina in rubber compositions can be shown, forexample, in U.S. Pat. No. 5,116,886 and EP 631,982.

[0069] The blocked mercaptosilane may be premixed, or prereacted, withthe filler particles or added to the rubber mix during the rubber andfiller processing, or mixing stage. If the silane and filler are addedseparately to the rubber mix during the rubber and filler mixing, orprocessing stage, it is considered that the blocked mercaptosilane thencombines in situ with the filler.

[0070] The vulcanized rubber composition should contain a sufficientamount of filler to contribute a reasonably high modulus and highresistance to tear. The combined weight of the filler may be as low asabout 5 to 100 phr, but is more preferably from 25 phr to 85 phr.

[0071] Precipitated silicas are preferred as the filler. The silica maybe characterized by having a BET surface area, as measured usingnitrogen gas, preferably in the range of 40 to 600 m²/g, and moreusually in a range of 50 to 300 m²/g. The silica typically may also becharacterized by having a dibutylphthalate (DBP) absorption value in arange of 100 to 350, and more usually 150 to 300. Further, the silica,as well as the aforesaid alumina and aluminosilicate, may be expected tohave a CTAB surface area in a range of 100 to 220. The CTAB surface areais the external surface area as evaluated by cetyl trimethylammoniumbromide with a pH of 9. The method is described in ASTM D 3849.

[0072] Mercury porosity surface area is the specific surface areadetermined by mercury porosimetry. For such technique, mercury ispenetrated into the pores of the sample after a thermal treatment toremove volatiles. Set up conditions may be suitably described as using a100 mg sample, removing volatiles during two hours at 105° C. andambient atmospheric pressure, ambient to 2000 bars pressure measuringrange. Such evaluation may be performed according to the methoddescribed in Winslow, Shapiro in ASTM bulletin, page 39 (1959) oraccording to DIN 66133. For such an evaluation, a CARLO-ERBA Porosimeter2000 might be used. The average mercury porosity specific surface areafor the silica should be in a range of 100 to 300 m²/g.

[0073] A suitable pore size distribution for the silica, alumina, andaluminosilicate according to such mercury porosity evaluation isconsidered herein to be: 5 percent or less of its pores have a diameterof less than about 10 nm; 60 percent to 90 percent of its pores have adiameter of 10 to 100 nm; 10 percent to 30 percent of its pores have adiameter of 100 to 1,000 nm; and 5 percent to 20 percent of its poreshave a diameter of greater than about 1,000 nm.

[0074] The silica might be expected to have an average ultimate particlesize, for example, in the range of 0.01 to 0.05 μm as determined by theelectron microscope, although the silica particles may be even smaller,or possibly larger, in size. Various commercially available silicas maybe considered for use in this invention such as, from PPG Industriesunder the HI-SIL trademark with designations HI-SIL 210, 243, etc.;silicas available from Rhone-Poulenc, with, for example, designation ofZEOSIL 1165MP; silicas available from Degussa with, for example,designations VN2 and VN3, etc.; and silicas commercially available fromHuber having, for example, a designation of HUBERSIL 8745.

[0075] Where it is desired for the rubber composition, which containsboth a siliceous filler such as silica, alumina and/or aluminosilicatesand also carbon black reinforcing pigments, to be primarily reinforcedwith silica as the reinforcing pigment, it is often preferable that theweight ratio of such siliceous fillers to carbon black is at least 3/1and preferably at least 10/1 and, thus, in a range of 3/1 to 30/1. Thefiller may be comprised of 15 to 95 weight percent precipitated silica,alumina, and/or aluminosilicate and, correspondingly 5 to 85 weightpercent carbon black, wherein the carbon black has a CTAB value in arange of 80 to 150. Alternatively, the filler can be comprised of 60 to95 weight percent of said silica, alumina, and/or aluminosilicate and,correspondingly, 40 to 5 weight percent carbon black. The siliceousfiller and carbon black may be preblended or blended together in themanufacture of the vulcanized rubber.

[0076] The rubber composition may be compounded by methods known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials.Examples of such commonly used additive materials include curing aids,such as sulfur, activators, retarders and accelerators, processingadditives, such as oils, resins including tackifying resins, silicas,plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes,antioxidants and antiozonants, peptizing agents, and reinforcingmaterials, such as, for example, carbon black. Depending on the intendeduse of the sulfur vulcanizable and sulfur vulcanized material (rubbers),the additives mentioned above are selected and commonly used inconventional amounts.

[0077] The vulcanization may be conducted in the presence of anadditional sulfur vulcanizing agent. Examples of suitable sulfurvulcanizing agents include, for example, elemental sulfur (free sulfur)or sulfur donating vulcanizing agents, for example, an amino disulfide,polymeric polysulfide, or sulfur olefin adducts which are conventionallyadded in the final, productive, rubber composition mixing step. Thesulfur vulcanizing agents (which are common in the art) are used, oradded in the productive mixing stage, in an amount ranging from 0.4 to 3phr, or even, in some circumstances, up to about 8 phr, with a range offrom 1.5 to 2.5 phr, sometimes from 2 to 2.5 phr, being preferred.

[0078] Vulcanization accelerators, i.e,, additional sulfur donors, maybe used herein. It is appreciated that they may be, for example, of thetype such as, for example, benzothiazole, alkyl thiuram disulfide,guanidine derivatives, and thiocarbamates. Representative of suchaccelerators are, for example, but are not limited to, mercaptobenzothiazole, tetramethyl thiuram disulfide, benzothiazole disulfide,diphenylguanidine, zinc dithiocarbamate, alkylphenoldisulfide, zincbutyl xanthate, N-dicyclohexyl-2-benzothiazolesulfenamide,N-cyclohexyl-2-benzothiazolesulfenamide,N-oxydiethylenebenzothiazole-2-sulfenamide, N,N-diphenylthiourea,dithiocarbamylsulfenamide, N,N-diisopropylbenzothiozole-2-sulfenamide,zinc-2-mercaptotoluimidazole, dithiobis(N-methyl piperazine),dithiobis(N-beta-hydroxy ethyl piperazine) and dithiobis(dibenzylamine). Other additional sulfur donors, may be, for example, thiuram andmorpholine derivatives. Representative of such donors are, for example,but not limited to, dimorpholine disulfide, dimorpholine tetrasulfide,tetramethyl thiuram tetrasulfide, benzothiazyl-2,N-dithiomorpholide,thioplasts, dipentamethylenethiuram hexasulfide, anddisulfidecaprolactam.

[0079] Accelerators are used to control the time and/or temperaturerequired for vulcanization and to improve the properties of thevulcanizate. In one embodiment, a single accelerator system may be used,i.e., a primary accelerator. Conventionally and preferably, a primaryaccelerator(s) is used in total amounts ranging from 0.5 to 4 phr,preferably 0.8 to 1.5 phr. Combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts (of 0.05 to 3 phr) in order to activate and to improvethe properties of the vulcanizate. Delayed action accelerators may beused. Vulcanization retarders might also be used. Suitable types ofaccelerators are amines, disulfides, guanidines, thioureas, thiazoles,thiurams, sulfenamides, dithiocarbamates, and xanthates. Preferably, theprimary accelerator is a sulfenamide. If a second accelerator is used,the secondary accelerator is preferably a guanidine, dithiocarbamate, orthiuram compound.

[0080] Typical amounts of tackifier resins, if used, comprise 0.5 to 10phr, usually 1 to 5 phr. Typical amounts of processing aids comprise 1to 50 phr. Such processing aids include, for example, aromatic,naphthenic, and/or paraffinic processing oils. Typical amounts ofantioxidants comprise 1 to 5 phr. Representative antioxidants may be,for example, diphenyl-p-phenylenediamine and others such as thosedisclosed in the Vanderbilt Rubber Handbook (1978), pages 344-46.Typical amounts of antiozonants comprise 1 to 5 phr. Typical amounts offatty acids, which, if used, can include stearic acid, comprise 0.5 to 3phr. Typical amounts of zinc oxide comprise 2 to 5 phr. Typical amountsof waxes comprise 1 to 5 phr. Often microcrystalline waxes are used.Typical amounts of peptizers comprise 0.1 to 1 phr. Typical peptizersmay be, for example, pentachlorothiophenol and dibenzamidodiphenyldisulfide.

[0081] The rubber composition of this invention can be used for variouspurposes. For example, it can be used for various tire compounds. Suchtires can be built, shaped, molded, and cured by various methods whichare known and will be readily apparent to those having skill in suchart.

[0082] All references cited are incorporated herein as they are relevantto the present invention.

[0083] The invention may be better understood by reference to thefollowing examples in which the parts and percentages are by weightunless otherwise indicated.

EXAMPLES Example 1 Preparation of 3-(methyldiacetoxysilyl)-1-propylthioacetate

[0084] A 5-liter flask was fitted with a 15-plate Oldershaw distillingcolumn (28 mm plate diameter), to which was attached a condenser anddistilling head capable of providing a controlled and adjustable refluxratio. Heat was supplied to the flask using an electric heating mantleregulated by a controller coupled to an electronic temperatureregulator. The vapor temperature in the head was monitored also. Thesystem was maintained under an atmosphere of nitrogen. Control of thevacuum was enhanced via a bleeder valve inserted between the cold trapand the distillation head.

[0085] 738.1 grams of 3-(methyldimethoxysilyl)-1-propyl mercaptan and1892.2 grams of acetic anhydride were added to the 5-liter flask. Themixture was heated with stirring until the first drops of liquid beganto collect from the head, at which time the collection rate was adjustedto 1-2 drops per second. Heat was supplied to the flask at a sufficientrate so as to maintain a reflux ratio of no less than 8:1, but notsufficient to cause column flooding. The collection temperature rapidlystabilized to 54° C. The collection rate was increased and adjusted tomaintain a collection temperature of not more than 55° C. until a totalof 506 grams of a clear, colorless liquid had been collected. Thedistillate had an odor of methyl acetate and was immiscible with andunresponsive toward aqueous sodium carbonate. Further distillation beganwith a collection at 54° C., with a gradual tendency toward highertemperatures and slower collection rates until a steady collection inthe range of 115° to 120° C. was maintained. 650 grams of a clear,colorless liquid was collected, which had an odor of acetic acid andmethyl acetate and demonstrated vigorous effervescence with aqueoussodium carbonate. After cooling, an additional 361 grams of aceticanhydride were added to the contents of the 5-liter flask, and thedistillation was reinitiated. Collection eventually stabilized at 140°C., yielding 493 grams of distillate. The temperature in the 5-literflask had risen to 180° C. whereupon the heating was stopped. Bothacetic acid and acetic anhydride could be detected in the distillate byodor. Its response with aqueous sodium carbonate was similar to theprevious sample. A final sample of distillate was collected undervacuum. The vacuum was regulated and maintained at the level required tocollect the distillate at a temperature near that of the cooling waterused to remove heat from the condenser using the bleeder valve. Thetemperature in the 5-liter flask was limited to 150° C. during thisprocedure. The bleeder valve gradually was opened. An additional 428grams of distillate collected. The final distillate had an odor ofacetic anhydride. At this point, the temperature in the 5-liter flaskwas slowly increased, leading to the fractional distillation of theproduct at <0.7 kPa. An initial 12-gram fraction was collected at <1drop/second with a reflux ratio of >10:1. A second fraction of 950 gramsof a clear, colorless liquid was collected at a substantially fasterrate with a reflux ratio of >5: 1. The distillation was terminated whenthe temperature of the 5-liter flask reached 180° C., leaving a darkbrown, viscous residue of 170 grams. The second fraction was product of98.5 percent purity (GC); distilled yield, 83 percent.

Example 2 Preparation of 3-(trimethoxysilyl)-1-propyl thioacetate

[0086] The apparatus used was identical to that of Example 1. 1,074grams of 3-(trimethoxysilyl)-1-propyl mercaptan and 561.4 grams ofacetic anhydride were added to the 5-liter flask. The system wasevacuated, followed by continuous application of vacuum using thebleeder valve in the nearly shut position. The temperature of the5-liter flask was increased gradually to 120° C., at which timecondensate began collecting at <30° C. The distillation was continueduntil nothing more collected with the 5-liter flask now at a temperatureof 155° C., at which time the heating was stopped, yielding 184 grams ofa clear, colorless liquid with a distinct odor of methyl acetate. Itsspecific gravity of 0.898 combined with a negative response to aqueoussodium carbonate indicated that a substantial portion of methanol wasprobably present. The temperature of the 5-liter flask was now graduallyraised to 195° C., yielding an additional total of 266 grams ofcondensate. The distillation was continued with gradual heating of the5-liter flask to 225° C. and with the bleeder valve open. 379 grams of aclear liquid was collected at a maximum head temperature of 104° C. GCanalysis indicated that both the starting and product silanes were majorcomponents of the distillate, with small amounts of acetic aciddetectable by odor.

[0087] The contents of the 5-liter flask were emptied into and stored ina 32-oz. (947 ml) bottle under nitrogen. The 5-liter flask was chargedwith the distillate, which was redistilled with the bleeder valve wideopen. A large first fraction contained mostly the starting blockedmercaptosilane. A second, clear and colorless 75 gram fraction wascollected at 70° C. This fraction was product of >90 percent purity(GC); distilled yield, 6 percent. The product also contained derivativecontaining methoxy-Si and acetoxy-Si groups and SiOSi crosslinks.

Example 3 Preparation of 3-(trimethoxysilyl)-1-propyl ThioacetateDerivative Containing Acetoxy-Si Groups and SiOSi Crosslinks

[0088] This product was the undistilled liquid that remained in thedistilling flask of Example 2 after removal of the second, clear andcolorless 75 gram fraction, which was collected at 70° C. and was theproduct of Example 2 of >90 percent purity (GC); distilled yield, 6percent.

Example 4 Preparation of 3-(trimethoxysilyl)-1-propyl ThioacetateDerivative Containing Acetoxy-Si Groups and SiOSi Crosslinks

[0089] The apparatus used was identical to that of Example 1. 1,775grams of 3-(trimethoxysilyl)-1-propyl mercaptan was added to the 5-literflask. A total of 4,719 grams of acetic anhydride was set aside forreaction with the mercaptosilane, of which 1,002 grams was added to the5-liter flask along with the mercaptosilane. The heat flow to the5-liter flask was increased gradually until a steady collection ofdistillate was established at a head temperature of 54° C. A total of840 grams of distillate was collected, which was found to contain methylacetate, acetic acid, and methanol in a 100/2/2.7 molar ratio by NMRanalysis. An additional 2,015 grams of acetic anhydride was added to thecooled 5-liter flask, and the distillation resumed, yielding anadditional 923 grams of distillate. The procedure was then repeated athird time with a 701 gram addition of acetic anhydride, yielding 834grams of distillate. The application of vacuum to the head was thenbegun. The vacuum was regulated and maintained at the level required tocollect the distillate at a temperature near that of the cooling waterused to remove heat from the condenser via the bleeder valve. Thetemperature in the 5-liter flask was limited to 170° C. during thisprocedure. The bleeder valve was opened gradually as the collection ratebegan to diminish. An additional 896 grams of distillate collected,whereupon any remaining liquids in the column and head evaporated. GCanalysis of the final distillate indicated that essentially nothing lessvolatile than acetic anhydride had distilled over. The contents of theflask cooled to a viscous, dark brown oil, which was stored undernitrogen.

Example 5 Preparation of 3-(propionylthio)-1-propyltrimethoxysilane

[0090] 816 grams of 3-mercapto-1-propyltrimethoxysilane, 871 grams of 25weight percent methanolic solution of sodium methoxide, and 1,724 gramsof toluene were charged to a 5-liter flask under an atmosphere ofnitrogen. The stirred mixture developed a pinkish color. Methanol wasremoved from the flask by distilling off a methanol-toluene azeotrope,during which time the contents of the flask turned colorless. Theappearance of a strong density current in the distillate which coincidedwith an increased in distillation head temperature from 63° C. to 108°C. signaled the point at which methanol removal from the flask wascomplete. With continued stirring, the contents of the flask wereallowed to cool and were placed in an ice-water bath. 361 grams ofpropionyl chloride was added to the flask dropwise and/or in smallportions with continued stirring in an ice-water bath until the reactionwas complete. Aliquots of the stirred mixture were taken periodicallyand placed onto pH paper. An alkaline reading indicated the completionof the reaction. The final mixture was a white suspension of NaCl in atoluene solution of the product. This mixture was filtered and thesolvent was removed from the filtrate to yield a light brown product.Gas chromatography indicated 5 percent3-mercapto-1-propyltrimethoxysilane, 25 percent of3-(methylthio)-1-propyltrimethoxysilane, and 70 percent of3-(acetylthio)-1-propyltrimethoxysilane (product). Flash distillationfrom one to two grams of powdered sodium methoxide yielded a colorlessproduct. The sodium methoxide was added to ensure that any remainingacidity was neutralized. Further optional fractional distillationyielded a product in excess of 98 percent purity by GC.

Example 6 Preparation of 3-(propionylthio)-1-propyltrimethoxysilane

[0091] 1,035 grams of 3-mercapto-1-propyltrimethoxysilane, 1,096 gramsof a 25 weight percent methanolic solution of sodium methoxide, and1,764 grams of toluene were charged to a 5-liter flask under anatmosphere of nitrogen. The stirred mixture developed a pinkish color.The flask was placed into a water bath at 64° C. Methanol was removedfrom the flask by distilling off a methanol-toluene azeotrope under apartial vacuum. The vacuum was kept such that the temperature in thedistillation head was maintained at 30° to 35° C. during which time1,500 ml of distillate, consisting of a toluene-methanol azeotrope, wascollected. During this time the contents of the flask turned colorless.An additional 429 grams of toluene were added, and the distillationresumed. The appearance of a strong density current in the distillate,which coincided with an increase in distillation head temperature from35° to 55° C., and the appearance of a changing liquid surface tensionin the condenser signaled the point at which methanol removal from theflask was complete. The contents of the flask had become a viscousfluid. With continued stirring, the contents of the flask were allowedto cool. The flask was placed in an ice-water bath, resulting in whatappeared to be a thick paste. 427 grams of propionyl chloride was addedto the flask dropwise and/or in small portions with continued stirringin an ice-water bath until the reaction was complete. Aliquots of thestirred mixture were taken periodically. An alkaline reading indicatedthe completion of the reaction. The final mixture was a white suspensionof NaCl in a toluene solution of the product. This mixture was filtered,and the solvent was removed from the filtrate to yield a nearlycolorless product. Gas chromatography indicated (by weight) 3 percent of3-mercapto-1-propyltrimethoxysilane, 1 percent of3-(methylthio)-1-propyltrimethoxysilane, and 96 percent of3-(acetylthio)-1-propyltrimethoxysilane (product). Flash distillationfrom one to two grams of powdered sodium methoxide yielded a colorlessproduct. The sodium methoxide was added to ensure that any remainingacidity was neutralized. Further optional fractional distillationyielded a product in excess of 98 percent purity by GC.

Example 7 Preparation of 3-(benzoylthio)-1-propyltriethoxysilane

[0092] 763 grams of 3-mercapto-1-propyltriethoxysilane and 1,013 gramsof a 21 weight percent ethanolic solution of sodium ethoxide werecharged to a 5-liter flask under an atmosphere of nitrogen. 850 grams ofethanol was distilled from this mixture at a maximum temperature of 45°C. at 48 kPa. 1,550 grams of toluene was added to the contents of theflask under nitrogen. The remaining ethanol was removed from the flaskby distilling off an ethanol-toluene azeotrope under a maximum absolutepressure of 48 kPa at a maximum temperature of 60° C. The vacuum waskept such that the temperature in the distillation head was maintainedat 30° to 40° C. The appearance of a strong density current in thedistillate which coincided with an increase in distillation headtemperature from 35° to about 60° C. and the appearance of a changingliquid surface tension in the condenser signaled the point at whichethanol removal from the flask was complete. At the end of thisprocedure the contents of the flask had become a clear, orange liquid.

[0093] With continued stirring, the contents of the flask were allowedto cool to ambient temperature. 418 grams of benzoyl chloride was addedto the flask dropwise and/or in small portions at a sufficiently slowrate to prevent the temperature from rising above 50° C. At thecompletion of the benzoyl chloride addition, stirring was continued foran additional day. The stirring was initially sufficiently vigorous tobreak up any chunks and inhomogeneities in the mixture. The resultingfinal mixture was a white suspension of NaCl in a toluene solution ofthe product. This mixture was filtered, and the solvent was removed fromthe filtrate to yield a light yellow-brown product which gave an acidicresponse to pH paper. Sufficient powdered sodium ethoxide was stirredinto the product to neutralize all of the acidity. Flash distillation at<0.7 kPa yielded a light pink product containing about 10 percent by gaschromatography each of ethyl benzoate and1-sila-2-thia-1,1-diethoxycyclopentane, which formed because of basecatalyzed decomposition during the distillation. A second flashdistillation was performed in which the first 30 percent of the productwas removed as a forecut. No base or acid was present. The secondfraction was a product of light pink color in excess of 98 percentpurity by GC.

Example 8 Preparation of 2-(acetylthio)-1-ethyltriethoxysilane

[0094] 2,513 grams of vinyltriethoxysilane was added to a 5-liter flaskand brought to reflux with stirring. A 25 ml forecut was distilled offto remove volatile impurities. The heating was stopped, and a first, 335gram, portion of a total of two portions of 1,005 grams of thiolaceticacid was added over a period of several minutes at a rate to maintain asmooth reflux. Heat was supplied toward the end of the addition, asnecessary, to maintain the reflux. 0.8 gram of di-t-butyl peroxide wasadded down the condensers, resulting in an immediate reaction asevidenced by a reflux rate acceleration. Power to the heating mantle wascut. During the reflux, the temperature rose to near 160° C. withinseveral minutes, whereupon the reflux subsided and the light yellowcontents of the pot began to cool.

[0095] When the contents of the pot had reached 150° C., an additional670 grams of thiolacetic acid was added in a manner similar to the firstaddition. 20 ml. of forecut were collected, and 1.6 grams of di-t-butylperoxide was again added. A slight increase in reflux rate was observedwithin several minutes. After 10 to 15 minutes, the pot reached amaximum temperature of 155° C. and subsequently began to cool. At 150°C. the temperature was maintained by the heating mantle for one hour.The pot was allowed to cool under nitrogen. Gas chromatography analysisindicated (by weight) 2 percent thiolacetic acid, 16 percentvinyltriethoxysilane, 5 percent 1-(acetylthio)-1-ethyltriethoxysilane(alpha adduct), 68 percent 2-(acetylthio)-1-ethyltriethoxysilane (betaadduct product), and 9 percent balance (mainly heavies).

Example 9 Preparation of 3-(octanoylthio)-1-propyltriethoxysilane

[0096] Into a 12-liter, three-necked round bottom flask equipped withmechanical stirrer, addition funnel, thermocouple, heating mantle, N₂inlet, and temperature controller were charged 1,021 grams of3-mercaptopropyltriethoxysilane (SILQUEST® A-1891 silane from OSiSpecialties, Inc., a subsidiary of Crompton Corp. of Greenwich, Conn.),433 grams of triethylamine, and 3,000 ml hexane. The solution was cooledin an ice bath, and 693 grams of octanoyl chloride were added over a twohour period via the addition funnel. After addition of the acid chloridewas complete, the mixture was filtered two times, first through a 0.1 μmfilter and then through a 0.01 μm filter, using a pressure filter, toremove the salt. The solvent was removed under vacuum. The remainingyellow liquid was vacuum distilled to yield 1,349 grams ofoctanoylthiopropyltriethoxysilane as a clear, very light yellow liquid.The yield was 87 percent.

Example 10 Preparation of 3-(acetylthio)-1-propyltriethoxysilane

[0097] This example illustrates the preparation of a thiocarboxylatealkoxysilane from a salt of a thiolcarboxylic acid using as a solventthe alcohol corresponding to the silane alkoxy group. Into a 250 ml,three-neck round bottomed flask equipped with magnetic stir bar,temperature probe/controller, heating mantle, addition funnel,condenser, and N₂ inlet was charged 63 grams of a 21 weight percentsodium ethoxide in ethanol. Fifteen grams of thiolacetic acid was addedslowly, keeping the temperature below 65° C. The solution was allowed tocool to room temperature, and 48 grams of chloropropyltriethoxysilanewas added via the addition funnel. After addition was complete, thesolution was heated to 70° C. for 24 hours whereupon a white solidformed. Analysis of the solution by gas chromatography showed a 78percent yield of acetylthiopropyltriethoxysilane.

Example 11 Preparation of Acetylthiomethyltriethoxysilane

[0098] This example illustrates the preparation of a thiocarboxylatealkoxysilane from a salt of a thiolcarboxylic acid using a nonproticsolvent. 88 grams of powdered sodium ethoxide and 600 ml diglyme werecharged into a one-liter, three-neck round bottomed flask equipped withmagnetic stir bar, temperature probe/controller, heating mantle,addition funnel, condenser, N₂ inlet, and ice water bath. The solutionwas cooled to 8° C., and 105 grams of thiolacetic acid was added slowlyvia the addition funnel, keeping the temperature below 60° C. Thesolution was allowed to cool to 35° C., and 250 grams ofchloromethyltriethoxysilane was added via the addition funnel. Afteraddition was complete, the solution was heated to 70° C., where a briefexotherm to 120° C. was observed. The solution was heated at 70° .C foran additional three hours. A white solid formed which was filtered firstthrough a 0.1 μm pressure filter and then a 0.01 μm filter to give aclear, black solution. The solvent was removed under reduced pressure,and the remaining liquid vacuum distilled to yield 163 grams of a clearand colorless liquid, a 55 percent yield.

Example 12 The Use of Silanes of Examples 1 to 4 in Low RollingResistant Tire Tread Formulation

[0099] A model low rolling resistance passenger tire tread formulationas described in Table 1 and a mix procedure were used to evaluaterepresentative examples of the silanes of the present invention. Thesilane in Example 1 was mixed as follows in a “B” BANBURY® (FarrellCorp.) mixer with a 103 cu. in. (1690 cc) chamber volume. The mixing ofthe rubber masterbatch was done in two steps. The mixer was turned onwith the mixer at 120 rpm and the cooling water on full. The rubberpolymers were added to the mixer and ram down mixed for 30 seconds. Halfof the silica and all of the silane with approximately 35-40 grams ofthis portion of silica in an ethylvinyl acetate (EVA) bag were added andran down mixed for 30 seconds. The remaining silica and the oil in anEVA bag were next added and ram down mixed for 30 seconds. The mixerthroat was thrice dusted down, and the mixture ram down mixed for 15seconds each time. The mixer's mixing speed was increased to 160 or 240rpm, as required to raise the temperature of the rubber masterbatch tobetween 160° and 165° C. in approximately one minute. The masterbatchwas dumped (removed from the mixer), a sheet was formed on a roll millset at about 50° to 60° C., and then allowed to cool to ambienttemperature.

[0100] The rubber masterbatch was added to the mixer with the mixer at120 rpm and cooling water turned on full and ram down mixed for 30seconds. The remainder of the ingredients was added and ram down mixedfor 30 seconds. The mixer throat was dusted down, the mixer speedincreased to 160 or 240 rpm so that the contents reached a temperaturebetween 160° and 165° C. in approximately two minutes. The rubbermasterbatch was mixed for eight minutes, and the speed of the BANBURYmixer as adjusted to maintain the temperature between 160° and 165° C.The masterbatch was dumped (removed from the mixer), a sheet was formedon a roll mill set at about 50° to 60° C., and then allowed to cool toambient temperature.

[0101] The rubber masterbatch and the curatives were mixed on a 6 in.×13in. (15 cm×33 cm) two roll mill that was heated to between 50° and 60°C. The sulfur and accelerators were added to the rubber masterbatch andthoroughly mixed on the roll mill and allowed to form a sheet. The sheetwas cooled to ambient conditions for 24 hours before it was cured. Therheological properties were measured on a Monsanto R-100 OscillatingDisk Rheometer and a Monsanto M1400 Mooney Viscometer. The specimens formeasuring the mechanical properties were cut from 6 mm plaques cured for35 minutes at 160° C. or from 2 mm plaques cured for 25 minutes at 160°C.

[0102] Silanes from Examples 2 to 4 were compounded into the tire treadformulation according to the above procedure. The performance of thesilanes prepared in Examples 1 to 4 was compared to the performance ofno silane coupling agent (Silane α), two silanes, one of which ispracticed in the prior art, bis-(3-triethoxysilyl-1-propyl)tetrasulfide(TESPT, Silane β), the other 3-triethoxysilyl-1-propylmercaptan (TESPM,Silane γ) which is the product resulting from the loss of a carboxylblocking group from a representative example of the silanes of thepresent invention. The results of this procedure are tabulated below inTable 2. TABLE 1 Model Low Rolling Resistance Tread Formulation PHRIngredient 75 sSBR (12% styrene, 46% vinyl, T_(g): 42° C.) 25 BR (98%cis, T_(g): 104° C.) 80 Silica (150-190 m²/gm, ZEOSIL 1165MP,Rhone-Poulenc) 32.5 Aromatic process oil (high viscosity, Sundex 8125,Sun) 2.5 Zinc oxide (KADOX 720C, Zinc Corp.) 1 Stearic acid (INDUSTRENE,Crompton) 2 6PPD antiozonant (SANTOFLEX 6PPD, Flexsys) 1.5Microcrystalline wax (M-4067, Schumann) 3 N330 carbon black (EngineeredCarbons) 1.4 Sulfur (#104, Sunbelt) 1.7 CBS accelerator (SANTOCURE,Flexsys) 2 DPG accelerator (PERKACIT DPG-C, Flexsys)

[0103] The following tests were conducted with the following methods (inall examples): Mooney Scorch @ 135° C. (ASTM Procedure D1646); MooneyViscosity @ 100° C. (ASTM Procedure D1646); Oscillating Disc Rheometer(ODR) @ 149° C., 1° arc, (ASTM Procedure D2084); Physical Properties,cured t90 @ 149° C. (ASTM Procedures D412 and D224) (G′ and G″ indynes/cm²); DIN Abrasion, mm³ (DIN Procedure 53516); and Heat Build(ASTM Procedure D623). TABLE 2 Performance of Representative Silanes ina Model Low Rolling Resistance Passenger Tire Tread Formulation Silane αβ Ex.4 Ex. 3 Ex. 1 Ex. 2 γ γ Amount — 7.4 7.4 7.4 7.4 8.3 3.8 6.35Mooney Viscosity at 100° C. ML1+4 130 67 65 58 73 63 74 121 MooneyScorch at 135° C. MS1+, t3, minutes 9.5 6.7 4.3 6.3 2.2 6.3 6.3 2.8MS1+, t18, 11.0 10.1 5.9 7.8 3.2 7.7 8.4 3.7 ODR @ 149° C., 10 arc, 30minute timer M_(L), dN-M 26.9 8.5 8.5 7.2 9.3 7.8 11.5 14.8 M_(H), dN-M44.5 30.8 31.0 31.4 34.8 30.5 27.8 33.9 t_(s)1, minutes 5.4 4.8 2.5 3.81.6 3.8 3.8 2.0 t90, minutes 10.5 17.8 8.0 8.0 8.1 7.5 15.3 15.0Physical Properties, cured t90 @ 149° C. Hardness, Shore A 66 57 59 6062 60 52 scorched Elongation, % 900 400 540 520 490 450 360 100% Mod.,kg/cm² 10.5 19.0 19.0 18.3 22.5 23.2 15.5 not 200% Mod., kg/cm² 15.556.9 49.2 46.4 59.8 66.1 45.0 cured 300% Mod., kg/cm² 24.6 128.0 101.296.2 116.0 129.4 104.8 Tensile, kg/cm² 137.1 208.1 234.8 218.0 237.6222.9 139.2 Dynamic Properties @ 0.15% strain, 10 Hz, torsion mode (2ndsweep) G′ @ 0° C., × 10⁷ 26.8 5.92 9.22 9.42 1.26 6.41 3.17 G′ @ 60° C.,× 10⁷ 12.7 2.76 4.26 3.89 5.36 3.02 1.75 G″ @ 0° C., × 10⁷ 2.87 1.261.81 1.84 2.14 1.3 5.69 G″ @ 60° C., × 10⁶ 11.2 2.48 4.00 3.85 4.94 2.712.13 Tan delta @ 0° C. 0.1070 0.2124 0.1968 0.1952 0.169 0.202 0.202 Tandelta @ 60° C. 0.0876 0.09 0.0939 0.0988 0.092 0.089 0.121 Ratio 0°C./60° C. 1.22 2.36 2.10 1.98 1.84 2.25 1.67 Heat Building-up, 100° C.ambient, 18.5% compression, 143 psi (99 kPa) load, 25 minutes Delta T, °C. 66 13 22 19 18 17 Set, % *** 6.3 10.9 8.8 8.0 6.9

Example 13 The Use of Silane of Example 1 in Low Rolling Resistance TireFormulation Activated by Varying Levels of DPG

[0104] The model low rolling resistance passenger tire tread formulationand mixing procedure of Example 11 were used to evaluate the silane ofExample 1 at three levels of N,N′-diphenylguanidine (DPG). The resultsare tabulated below in Table 3. TABLE 3 The Effect of DPG on theCompounding and Curing of a Model Low Rolling Resistance Passenger TireTread Formulation Run A B C phr DPG 2.00 0.5 1.25 Mooney viscosity @100° C. ML 1 + 4 75 — — Mooney scorch @ 135° C. M_(V) 41 — — MS 1+, t₃,minutes 2.5 15.3 6.2 MS 1+, t₁₈, minutes 3.6 24.1 8.3 ODR @ 149° C., 1°arc, 30 minute timer M_(L), dN-M 9.8 9.4 8.6 M_(H), dN-M 35.7 28.8 33.4t_(s)1, minutes 1.8 8.0 3.4 t90, minutes 8.0 22.5 11.8 Physicalproperties, cured t90 @ 149° C. Hardness, Shore A 63 59 62 Elongation, %550 620 560 100% Modulus, kg/cm² 21.1 19.0 22.5 200% Modulus, kg/cm²55.5 42.9 55.5 300% Modulus, kg/cm² 106.9 80.9 106.2 Tensile, kg/cm² 236209.5 234.1 DIN Abrasion, mm³ 85 69 72 SIL0007-6 Dynamic properties @ 10Hz, 0.15 strain, torsion mode G′ @ 0° C., × 10⁷ 14.8 14.1 12.6 G′ @ 60°C., × 10⁷ 6.23 5.97 5.64 G″ @ 0° C., × 10⁷ 23.0 26.4 22.1 G″ @ 60° C., ×10⁶ 6.55 7.30 6.01 Tan delta @ 0° C. 0.1551 0.1872 0.1753 Tan delta @60° C. 0.1053 0.1189 0.1035 Ratio 0° C./60° C. 1.47 1.57 1.69

Example 14 Shoe Sole Compound Compositions

[0105] Formulation: 60 Budene 1207 BR, 40 SMR5L NR, 45 ZEOSIL 1165MPSilica, 5 CALSOL 5550 Process Oil, 3 CARBOWAX 3350 PEG, 5 KADOX 720CZinc Oxide, 1 INDUSTRENE R Stearic Acid, 1 BHT Antioxidant, 1 SUNOLITE240 Wax, 1.9 Rubbermakers Sulfur 104, 1.3 MBTS, 0.5 MBT, 0.2 TMTM,Silane—SILQUEST A-1289 silane (TESPT) or acetylthiopropyltriethoxysilane(Acetyl). The amounts of each are in phr. The term “Add Sulfur” or “AddS” means that additional sulfur was added to make the amount of sulfurin the Acetyl equivalent to the amount of sulfur delivered by TESPT. Theresults are set forth in Table 4 below. TABLE 4 Silane None TESPT TESPTAcetyl Acetyl Acetyl Acetyl Add Sulfur — — — — X — X Amount, phr — 2 4 22 4 4 Mooney Scorch at 135° C. MV 51 42 40 36 33 MS1+, t₃, minutes 5.04.3 4.3 6.9 7.4 MS1+, t₁₈, minutes 5.8 5.3 5.3 8.2 8.8 Mooney Viscosity@ 100° C. ML1 + 4 96 78 76 74 71 ODR @ 149° C., 1° arc, 12 minute timerM_(L), dN-M 19.7 14.9 14.0 12.2 11.5 10.4 10.2 M_(H), dN-M 59.7 57.454.2 52.0 52.8 49.3 49.8 t_(s)1, minutes 3.5 2.8 2.8 4.3 3.8 4.7 4.4t90, minutes 5.7 5.6 5.9 7.5 7.1 8.2 8.2 Physical Properties, cured t90@ 149° C. Hardness, Shore A 67 67 66 66 66 66 66 Elongation, % 630 570570 540 440 500 460 100% Mod., kg/cm² 19.7 23.9 25.3 26.7 26.7 26.7 27.4200% Mod., kg/cm² 36.6 50.6 54.1 56.2 59.1 55.5 59.8 300% Mod., kg/cm²58.3 86.5 91.4 97.7 103.3 96.3 105.5 Tensile, kg/cm² 187.0 204.6 222.2201.1 174.4 189.8 189.1 DIN Abrasion, mm³ 86 75 67 74 71 65 73 AkronAbrasion, mm³ 0.46 0.48 0.35 0.39 0.41 0.45 0.44

Example 15 Low Rolling Resistance Tire Formulations

[0106] The following silanes were tested in low rolling resistance tireformulations; TESPT (A); TESPM (B);3-acetylthio-1-propyltrimethoxysilane (C),3-acetylthio-1-propyltriethoxysilane (D),3-octanoylthio-1-propyltriethoxysilane (E);3-palmitoylthio-1-propyltriethoxysilane (F);3-ethylhexanoyl-1-propyltriethoxysilane (G);3-propionylthio-1-propyltrimethoxysilane (H);3-benzoylthio-1-propyltriethoxysilane (I);acetylthiomethyltriethoxysilane (J), acetylthioethyltrimethoxysilane(K), acetylthioethyltriethoxysilane (L),acetothioethylmethyldimethoxysilane (M), acetylthiooctyltrimethoxysilane(N), acetylthiooctyltriethoxysilane (O),acetylthiocyclohexylethyltrimethoxysilane (P), andacetothionorbornylethyltrimethoxysilane (Q). The formulation was(amounts in phr) 75 SOLFLEX 1216 sSBR, 25 Budene 1207 BR, 80 ZEOSIL1165MP silica, 32.5 SUNDEX 3125 process oil, 2.5 KADOX 720C zinc oxide,1.0 INDUSTRENE R stearic acid, 2.0 SANTOFLEX 13 antiozonant, 1.5 M4067microwax, 3.0 N330 carbon black, 1.4 Rubbermakers sulfur 104, 1.7 CBS,2.0 DPG, Silane as shown. TABLE 5 Silane A B B C C D D Add S X X XAmount, phr 7.0 6.36 6.36 6.33 6.33 7.45 7.45 Mooney Viscosity at 100°C. ML1 + 4 94 74 74 72 — 62 — Mooney Scorch at 135° C. MS1+, t₃, minutes6.2 9.9 9.0 6.9 7.5 6.3 6.3 MS1+, t₁₈, minutes 8.9 12.6 11.5 9.3 10.27.6 7.8 ODR @ 149° 0 C., 1° arc, 30 minute timer M_(L), dN-M 9.6 8.1 8.18.7 8.5 7.9 7.7 M_(H), dN-M 31.8 29.5 34.5 32.0 36.7 29.9 33.9 t_(s)1,minutes 4.5 5.4 5.1 4.1 4.5 3.6 3.5 t90, minutes 17.6 10.4 14.1 11 11.58.0 7.5 Physical Properties, cured t90 @ 149° C. Hardness, Shore A 57 5860 64 66 59 60 Elongation, % 420 560 440 660 570 630 540 100% Mod.,kg/cm² 20.4 16.9 22.5 17.6 22.5 15.5 19.0 200% Mod., kg/cm² 58.4 40.159.8 38.7 54.8 34.5 49.9 300% Mod., kg/cm² 123.7 84.4 123.0 73.8 105.571.7 104.1 Tensile, kg/cm² 210.9 210.3 211.6 225.0 250.3 223.6 236.2 DINAbrasion mm³ 71 69 76 114 97 131 90 Heat Build-up @ 100° C., 17.5%compression, 99 kPa static, 25 minute run Delta T, ° C. 13.3 18.9 13.332.2 18.3 21.1 13.3 Permanent set, % 6.2 10.5 6.3 25.3 12.3 14.5 9.8Dynamic Properties @ 0.15% strain, 10 Hz, torsion mode G′ @ 0° C.,dyn/cm² × 10⁷ 6.73 12.8 12.4 20.1 16.6 12.8 10.4 G′ @ 60° C., dyn/cm² ×10⁷ 3.00 5.13 5.15 8.73 2.67 5.10 1.93 G″ @ 0° C., dyn/cm² × 10⁷ 1.462.44 2.43 3.39 7.06 2.47 4.05 G″ @ 60° C., dyn/cm² × 10⁷ 2.93 5.23 4.478.35 5.33 5.79 3.21 TAN delta @ 0° C. 0.216 0.191 0.196 0.168 0.1610.192 0.185 TAN delta @ 60° C. 0.098 0.102 0.087 0.096 0.075 0.114 0.079Ratio 0° C./60° C. 2.22 1.88 2.26 1.75 2.15 1.68 2.34 Silane E E F F G HH Add S X X X Amount, ph 9.69 12.67 12.67 9.62 6.7 6.7 Mooney Viscosityat 100° C. ML1 + 4 55 — 50 — 52 66 — Mooney Scorch, at 135° C. MS1+, t₃,minutes 10.4 9.6 13.0 11.9 16.8 8.3 7.7 MS1+, t₁₈, 11.7 11.7 14.6 13.919.0 9.9 9.6 ODR @ 149° C., 1° arc, 30 minute timer M_(L), dN-M 6.7 6.85.7 5.7 5.5 8.2 7.9 M_(H), dN-M 27.8 32.3 26.8 30.7 31.6 30.1 34.6t_(s)1, minutes 5.6 5.5 7.0 6.8 9.1 4.5 4.4 t90, minutes 11.3 9.8 12.311.0 14.1 9.5 9.0 Physical Properties, cured t90 @ 149° C. Hardness,Shore A 53 55 51 54 56 58 60 Elongation, % 600 490 740 610 600 610 540100% Mod., kg/cm² 14.1 17.6 12.7 15.5 15.5 16.2 20.4 200% Mod., kg/cm²34.5 49.2 27.4 36.6 35.9 38.0 52.7 300% Mod., kg/cm² 77.3 105.5 55.571.0 69.6 80.2 108.3 Tensile, kg/cm² 227.8 213.7 205.3 186 175.8 234.1244.7 DIN Abrasion mm³ 99 92 — — 157 127 94 Heat Build-up @ 100° C.,17.5% compression, 99 kPA static, 25 minute run Delta T, ° C. 12.2 8.9 —— 10.5 18.9 12.21 Permanent set, % 5.0 4.6 — — 7.0 11.0 7.7 DynamicProperties @ 0.15% strain, 10 Hz, torsion mode G′ @ 0° C., dyn/cm² × 10⁷4.80 4.62 6.40 5.93 9.29 10.1 9.54 G′ @ 60° C., dyn/cm² × 10⁷ 2.44 0.822.42 1.13 1.88 4.18 1.76 G″ @ 0° C., dyn/cm² × 10⁷ 0.98 2.00 1.27 2.173.64 2.07 3.72 G″ @ 60° C., dyn/cm² × 10⁶ 2.14 1.27 2.34 1.23 3.08 4.622.72 Tan delta @ 0° C. 0.205 0.177 0.199 0.191 0.202 0.205 0.184 Tandelta @ 60° C. 0.088 0.064 0.097 0.057 0.085 0.110 0.073 Ratio 0° C./60°C. 2.33 2.77 2.05 3.35 2.39 1.86 2.52 Silane I J K K L L M M Add S X X XAmount, phr 9.1 6.7 5.96 5.96 7.08 7.08 5.54 5.54 Mooney Viscosity at100° C. ML1 + 4 55 69 73 — 63 — 71 — Mooney Scorch at 135° C. MS1+, t₃,minutes 11.5 2.5 4.6 4.3 4.5 4.6 4.7 4.9 MS1+, t₁₈, 13.5 3.5 5.6 5.6 5.35.6 5.8 6.1 ODR @ 149° C., 1° arc, 30 minute timer M_(L), dN-M 6.2 8.89.5 9.0 6.8 7.7 9.4 9.3 M_(H), dN-M 35.0 32.5 29.8 34.1 27.5 31.3 33.938.1 t_(s)1, minutes 6.3 1.9 2.8 2.8 2.8 2.8 3.0 2.9 t90, minutes 11.317.0 16.8 15.3 11.3 9.5 13.5 11.8 Physical Properties, cured t90 @ 149°C. Hardness, Shore A 62 61 61 65 56 58 66 65 Elongation, % 560 440 500470 580 560 530 530 100% Mod., kg/cm² 19.0 19.0 19.0 20.4 14.8 17.6 21.222.5 200% Mod., kg/cm² 47.8 51.3 43.6 51.3 33.7 42.9 47.1 55.5 300%Mod., kg/cm² 107.5 109.0 84.4 105.5 69.6 91.4 87.9 105.5 Tensile, kg/cm²210.9 198.2 184.9 208.1 199.0 234.8 196.9 225.7 Silane I J K K L L M DINAbrasion mm³ 133 88 113 103 133 96 101 Heat Build-up @ 100° C., 17.5%compression, 99 kPa static, 25 minute run Delta T, ° C. 12.8 15.6 21.716.1 28.9 16.7 25.0 Permanent set, % 7.9 10.8 13.7 8.7 23.2 11.2 17.3Dynamic Properties @ 0.15% strain, 10 Hz, torsion mode G′ @ 0° C.,dyn/cm² × 10⁷ 17.9 10.8 18.2 16.1 10.1 8.94 27.7 G′ @ 60° C., dyn/cm² ×10⁷ 2.99 2.16 6.60 2.70 4.30 1.73 9.54 G″ @ 0° C., dyn/cm² × 10⁷ 6.383.92 3.27 5.86 2.12 3.65 4.33 G″ @ 60° C., dyn/cm² × 10⁶ 6.83 4.87 9.415.92 5.32 2.92 14.0 Tan delta @ 0° C. 0.167 0.201 0.180 0.167 0.2100.193 0.156 Tan delta @ 60° C. 0.107 0.124 0.143 0.101 0.124 0.080 0.147Ratio 0° C./60° C. 1.56 1.67 1.26 1.65 1.69 2.41 1.06 Silane M N N O O PQ DIN Abrasion mm³ 96 100 94 113 97 141 132 Heat Build-up @ 100° C.,17.5% compression, 99 kPa static, 25 minute run Delta T, ° C. 16.7 21.115.6 14.4 10.0 17.2 15.0 Permanent set, % 9.2 16.8 12.6 11.0 7.5 12.710.8 Dynamic Properties @ 0.15% strain, 10 Hz, torsion mode G′ @ 0° C.,dyn/cm² × 10⁷ 22.2 14.9 12.4 10.2 8.10 27.6 23.8 G′ @ 60° C., dyn/cm² ×10⁷ 3.39 5.72 2.33 4.25 1.55 3.72 3.59 G″ @ 0° C., dyn/cm² × 10⁷ 7.792.93 4.85 2.06 2.80 10.8 9.04 G″ @ 60° C., dyn/cm² × 10⁶ 9.17 5.75 3.624.06 2.44 12.4 9.61 Tan delta @ 0° C. 0.153 0.197 0.187 0.202 0.1920.135 0.151 Tan delta @ 60° C. 0.118 0.101 0.075 0.096 0.087 0.115 0.106Ratio 0° C./60° C. 1.30 1.95 2.49 2.10 2.21 1.18 1.42

What is claimed is:
 1. A rubber composition comprising: a) a blockedmercaptosilane selected from the group consisting of:[[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G—(SiX₃)_(s)  (1);  and[(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)  wherein Y is apolyvalent species (Q)_(Z)A(═E), each wherein the atom A attached to theunsaturated hetero atom E is attached to the sulfur, which in turn islinked via a group G to the silicon atom; each R is chosen independentlyfrom hydrogen, straight, cyclic or branched alkyl that may or may notcontain unsaturation, alkenyl groups, aryl groups, and aralkyl groups,with each R containing from 1 to 18 carbon atoms; each G isindependently a monovalent or polyvalent group derived by substitutionof alkyl, alkenyl, aryl or aralkyl wherein G can contain from 1 to 18carbon atoms, with the proviso that if Y is —C(═O)—, G is not such thatthe blocked mercaptosilane would contain an α,β-unsaturated carbonyl,and if G is univalent, G can be a hydrogen atom; X is independently agroup selected from the group consisting of —Cl, —Br, RO—, RC(═O)O—,R₂C═NO—, R₂NO—, R₂N—, —R, and —(OSiR₂)_(t)(OSiR₃) wherein each R is asabove and at least one X is not —R; Q is oxygen, sulfur or (—NR—); A iscarbon, sulfur, phosphorus, or sulfonyl; E is oxygen, sulfur or NR; p is0 to 5; r is 1 to 3; z is 0 to 2; q is 0 to 6; a is 0 to 7; b is 1 to 3;j is 0 to 1, but it may be 0 only if p is 1; c is 1 to 6; t is 0 to 5; sis 1 to 3; k is 1 to 2, with the provisos that (A) if A is carbon,sulfur or sulfonyl, then (i) a+b is 2 and (ii) k is 1; (B) if A isphosphorus, then a+b is 3 unless both (i) c is greater than 1 and (ii) bis 1, in which case a is c+1; and (C) if A is phosphorus, then k is 2;b) an organic polymer; and c) a filler.
 2. The rubber composition ofclaim 1 wherein the blocked mercaptosilane is selected from the groupconsisting of: 2-triethoxysilyl-1-ethyl thioacetate;2-trimethoxysilyl-1-ethyl thioacetate; 2-(methyldimethoxysilyl)-1-ethylthioacetate; 3-trimethoxysilyl -1-propyl thioacetate;triethoxysilylmethyl thioacetate; trimethoxysilylmethyl thioacetate;triisopropoxysilylmethyl thioacetate; methyldiethoxysilylmethylthioacetate; methyldimethoxysilylmethyl thioacetate;methyldiisopropoxysilylmethyl thioacetate; dimethylethoxysilylmethylthioacetate; dimethylmethoxysilylmethyl thioacetate; dimethylisopropoxysilylmethyl thioacetate; 2-thriisopropoxysilyl-1-ethyl thioacetate;2-(methyldiethoxysilyl)-1-ethyl thioacetate, 2-(methydiisopropoxysilyl)-1-ethyl tioacetate ; 2-(dimethylethoxysilyl-)-1-ethyl thioacetate;2-(dimethylmethoxysilyl)-1-ethyl thioacetate;2-(dimethylisopropoxysilyl)-1-ethyl thioacetate;3-triethoxysilyl-1-propyl thioacetate; 3-triisopropoxysilyl-1-propylthioacetate; 3-methyldiethoxysilyl-1-propyl thioacetate;3-methyldimethoxysilyl-1-propyl thioacetate;3-methyldiisopropoxysilyl-1-propyl thioacetate;1-(2-triethoxysilyl-1-ethyl)-4-thioacetylcyclohexane;1-(2-triethoxysilyl-1-ethyl)-3-thioacetylcyclohexane;2-triethoxysilyl-5-thioacetylnorbornene;2-triethoxysilyl-4-thioacetylnorbornene;2-(2-triethoxysilyl-1-ethyl)-5-thioacetylnorbornene;2-(2-triethoxysilyl-1-ethyl)-4-thioacetylnorbornene;1-(1-oxo-2-thia-5-triethoxysilylpenyl)benzoic acid;6-triethoxysilyl-1-hexyl thioacetate; 1-triethoxysilyl-5-hexylthioacetate; 8-triethoxysilyl-1-octyl thioacetate;1-triethoxysilyl-7-octyl thioacetate; 6-triethoxysilyl-1-hexylthioacetate; 1-triethoxysilyl-5-octyl thioacetate;8-trimethoxysilyl-1-octyl thioacetate; 1-trimethoxysilyl-7-octylthioacetate; 1 0-triethoxysilyl-1-decyl thioacetate;1-triethoxysilyl-9-decyl thioacetate; 1-triethoxysilyl-2-butylthioacetate; 1-triethoxysilyl-3-butyl thioacetate;1-triethoxysilyl-3-methyl-2-butyl thioacetate;1-triethoxysilyl-3-methyl-3-butyl thioacetate;3-trimethoxysilyl-1-propyl thiooctanoate;3-triethoxysilyl-1-propyl-1-propyl thiopalmitate;3-triethoxysilyl-1-propyl thiooctanoate; 3-triethoxysilyl-1-propylthiobenzoate; 3-triethoxysilyl-1-propyl thio-2-ethylhexanoate;3-methyldiacetoxysilyl-1-propyl thioacetate; 3-triacetoxysilyl-1-propylthioacetate; 2-methyldiacetoxysilyl-1-ethyl thioacetate;2-triacetoxysilyl-1-ethyl thioacetate; 1-methyldiacetoxysilyl-1-ethylthioacetate; 1-triacetoxysilyl-1-ethyl thioacetate;tris-(3-triethoxysilyl-1-propyl)trithiophosphate;bis-(3-triethoxysilyl-1-propyl)methyldithiophosphonate;bis-(3-triethoxysilyl-1-propyl)ethyldithiophosphonate;3-triethoxysilyl-1-propyldimethylthiophosphinate;3-triethoxysilyl-1-propyldiethylthiophosphinate;tris-(3-triethoxysilyl-1-propyl)tetrathiophosphate;bis-(3-triethoxysilyl-1-propyl)methyltrithiophosphonate;bis-(3-triethoxysilyl-1-propyl)ethyltrithiophosphonate;3-triethoxysilyl-1-propyldimethyldithiophosphinate;3-triethoxysilyl-1-propyldiethyldithiophosphinate;tris-(3-methyldimethoxysilyl-1-propyl)trithiophosphate;bis-(3-methyldimethoxysilyl-1-propyl)methyldithiophosphonate;bis-(3-methyldimethoxysilyl-1-propyl)ethyldithiophosphonate;3-methyldimethoxysilyl-1-propyldimethylthiophosphinate;3-methyldimethoxysilyl-1-propyldiethylthiophosphinate;3-triethoxysilyl-1-propylmethylthiosulphate;3-triethoxysilyl-1-propylmethanethiosulphonate;3-triethoxysilyl-1-propylethanethiosulphonate;3-triethoxysilyl-1-propylbenzenethiosulphonate;3-triethoxysilyl-1-propyltoluenethiosulphonate;3-triethoxysilyl-1-propylnaphthalenethiosulphonate;3-triethoxysilyl-1-propylxylenethiosulphonate;triethoxysilylmethylmethylthiosulphate;triethoxysilylmethylmethanetbiosulphonate;triethoxysilylmethylethanethiosulphonate;triethoxysilylmethylbenzenethiosulphonate;triethoxysilylmethyltoluenethiosulphonate;triethoxysilylmethylnaphthalenethiosulphonate; andtriethoxysilylmethylxylenethiosulphonate.
 3. The rubber composition ofclaim 1 wherein Y is —C(═O)—.
 4. The rubber composition of claim 3wherein the silane is of formula (1), each X is RO—, r is 1, and s is 1.5. The rubber composition of claim 1 wherein G, which is directly bondedto Y, is alkyl of two to twelve carbon atoms.
 6. The rubber compositionof claim 1 wherein G, which is directly bonded to Y, is alkyl of six toeight carbon atoms.
 7. A rubber composition comprising: a) a blockedmercaptosilane selected from the group consisting of: ti[[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G(SiX₃)_(s)  (1);  and[(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)  wherein Y is apolyvalent species (Q)_(Z)A(═E) selected from the group consisting of—C(═NR)—; —SC(═NR)—; —SC(═O)—; —OC(═O)—; —S(═O)—; —S(═O)₂—; —OS(═O)₂—;(═NR)S(═O)₂—; —SS(═O)—; —OS(═O)—; (═NR)S(═O)—; —SS(═O)₂—; (—S)₂P(═O)—;(═NR)(—S)P(═O)—; (—O)(—NR)P(═O)—; (—O)(—S)P(═O)—; (—O)₂P(═O)—;—(—O)P(═O)—; —(—NR)P(═O)—; (═NR)₂P(═S)—; (—NR)(—S)P(═S)—;(—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—; —(—O)P(═S)—; and—(—NR)P(═S)—; wherein the atom A, attached to the unsaturated heteroatomE, is attached to the sulfur, which, in turn, is linked via a group G tothe silicon atom; each R is chosen independently from hydrogen,straight, cyclic, or branched alkyl that may or may not containunsaturation, alkenyl groups, aryl groups, and aralkyl groups, with eachR containing from 1 to 18 carbon atoms; each G is independently amonovalent or polyvalent group derived by substitution of alkyl,alkenyl, aryl, or aralkyl wherein G can contain from 1 to 18 carbonatoms, with the proviso that G is not such that the blockedmercaptosilane would contain an α,β-unsaturated carbonyl, and if G isunivalent, G can be a hydrogen atom; X is independently selected fromthe group consisting of —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—,—R, and —(OSiR₂)_(t)(OSiR₃) wherein each R is as above and at least oneX is not —R; p is 0 to 5; r is 1 to 3; z is 0 to 2; q is 0 to 6; a is 0to 7; b is 1 to 3; j is 0 to 1, but it may be 0 only if p is 1; c is 1to 6; t is 0 to 5; s is 1 to 3; k is 1 to 2; with the provisos that (I)if A is carbon, sulfur, or sulfonyl, then (i) a+b is 2 and (ii) k is 1;(II) if A is phosphorus, then a+b is 3 unless both (i) c is greater than1 and (ii) b is 1, in which case a is c+1; and (III) if A is phosphorus,then k is 2; b) an organic polymer; and c) a filler.
 8. The rubbercomposition of claim 7 wherein each R is independently selected from thegroup consisting of methyl, ethyl, propyl, isobutyl, phenyl, tolyl,phenethyl, norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl,ethylcyclohexyl, ethylcyclohexenyl, and cyclohexylcyclohexyl.
 9. Therubber composition of claim 7 wherein the blocked mercaptosilane has theformula: [[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G(SiX₃)_(s).
 10. Therubber composition of claim 7 wherein the blocked mercaptosilane has theformula: [(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c).
 11. The rubbercomposition of claim 7 wherein the blocked mercaptosilane is partiallyhydrolyzed.
 12. The rubber composition of claim 7 wherein Y is selectedfrom the group consisting of —OC(═O)—; —SC(═O)—; —S(═O)—; —OS(═O)—;—(—S)P(═O)—; and —P(═O)(−)₂.
 13. The rubber composition of claim 7wherein each G is selected from the group consisting of a substitutedphenyl and a substituted straight chain alkyl having from 2 to 12 carbonatoms.
 14. The rubber composition of claim 7 wherein X is independentlyselected from the group consisting of methoxy, ethoxy, isobutoxy,propoxy, isopropoxy, acetoxy, and oximato.
 15. A rubber compositioncomprising: a) a blocked mercaptosilane selected from the groupconsisting of: [[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G(SiX₃)_(s)  (1); and [(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)  wherein Y is apolyvalent species (Q)_(Z)A(═E) selected from the group consisting of—C(═NR)—; —SC(═NR)—; —SC(═O)—; —OC(═O)—; —S(═O)—; —S(═O)₂—; —OS(═O)₂—;(—NR)S(═O)₂—; —SS(═O)—; —OS(═O)—; (—NR)S(═O)—; —SS(═O)₂—; (—S)₂P(═O)—;—(—S)P(═O)—; —P(═O)(−)₂; (—S)₂P(═S)—; —(—S)P(═S)—; —P(═S)(−)₂;(—NR)₂P(═O)—; (—NR)(—S)P(═O)—; (—O)(—NR)P(═O)—; (—O)(—S)P(═O)—;(—O)₂P(═O)—; —(—O)P(═O)—; —(—NR)P(═O)—; (—NR)₂P(═S)—; (—NR)(—S)P(═S)—;(—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—; —(—O)P(═S)—; and—(—NR)P(═S)—; wherein the atom A, attached to the unsaturated heteroatomE, is attached to the sulfur which in turn is linked via a group G tothe silicon atom; each R is independently selected from the groupconsisting of hydrogen, phenyl, isopropyl, cyclohexyl, and isobutyl;each G is independently selected from the group consisting of asubstituted phenyl and a substituted straight chain alkyl having from 2to 12 carbon atoms; X is independently selected from the groupconsisting of RO— and RC(═O)O—, wherein each R is as above; p is 0 to 2;r is 1 to 3;z is 0 to 2; q is 0 to 6; a is 0 to 7; b is 1 to 3; j is 0to 1, but it may be 0 only if p is 1; c is 1 to 6; t is 0 to 5; s is 1to 3; k is 1 to 2; with the provisos that (I) if A is carbon, sulfur orsulfonyl, then (i) a+b is 2 and (ii) k is 1; (II) if A is phosphorus,then a+b is 3 unless both (i) c is greater than 1 and (ii) b is 1, inwhich case a is c+1; and (III) if A is phosphorus, then k is 2; b) anorganic polymer; and c) a filler.
 16. The rubber composition of claim 15wherein X is selected from the group consisting of methoxy, ethoxy, andacetoxy.
 17. A rubber composition comprising: a) a blockedmercaptosilane selected from the group consisting of:[[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G(SiX₃)_(s)  (1);  and[(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)  wherein Y is —C(═O)—;each R is independently selected from the group consisting of hydrogen,phenyl, and an alkyl having from three to six carbon atoms; each G isindependently selected from the group consisting of a substituted phenyland a substituted straight chain alkyl having from 2 to 12 carbon atoms,with the proviso that G is not such that the blocked mercaptosilanewould contain an α,β-unsaturated carbonyl including a carbon-carbondouble bond next to the thiocarbonyl group that can undergopolymerization reactions; X is independently selected from the groupconsisting of —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, and —R,wherein each R is as above and at least one X is not —R; and p is 2 to5; r is 1 to 3; q is 0 to 6; a is 0 to 7; b is 1 to 2; j is 1; c is 1 to6; s is 1 to 3; k is 1; and a+b is 2; b) an organic polymer; and c) afiller.
 18. The rubber composition of claim 17 wherein R is selectedfrom the group consisting of phenyl, isopropyl, cyclohexyl, andisobutyl.
 19. The rubber composition of claim 17 wherein G is asubstituted straight chain alkyl having 3 to 12 carbon atoms.
 20. Therubber composition of claim 17 wherein G is a substituted phenyl. 21.The rubber composition of claim 17 wherein X is selected from the groupconsisting of methoxy, ethoxy, isobutoxy, propoxy, isopropoxy, acetoxy,and oximato.
 22. A rubber composition comprising a blockedmercaptosilane of the formula: X₃SiGSC(═O)GC(═O)SGSiX₃ wherein each R ischosen independently from hydrogen, straight, cyclic, or branched alkylthat may or may not contain unsaturation, alkenyl groups, aryl groups,and aralkyl groups, with each R containing from 1 to 18 carbon atoms;each G is independently a divalent group derived by substitution ofalkyl, alkenyl, aryl, or aralkyl, wherein G can contain from 1 to 18carbon atoms, with the proviso that G is not such that the blockedmercaptosilane would contain an α,β-unsaturated carbonyl including acarbon-carbon double bond next to the thiocarbonyl group; X isindependently selected from the group consisting of —Cl, —Br, RO—,RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, —R, and —(OSiR₂)_(t)(OSiR₃) wherein eachR is as above and at least one X is not —R; and t is 0 to
 5. 23. Anarticle of manufacture comprising a rubber composition comprising: a) ablocked mercaptosilane selected from the group consisting of:[[(ROC(═O))_(p)—(G)_(j)]_(k)—Y—S]_(r)—G—(SiX₃)_(s)  (1);  and[(X₃Si)_(q)—G]_(a)—[Y—[S—G—SiX₃]_(b)]_(c)  (2)  wherein Y is apolyvalent species (Q)_(Z)A(═E), each wherein the atom A attached to theunsaturated heteroatom E is attached to the sulfur, which in turn islinked via a group G to the silicon atom; each R is chosen independentlyfrom hydrogen, straight, cyclic, or branched alkyl that may or may notcontain unsaturation, alkenyl groups, aryl groups, and aralkyl groups,with each R containing from 1 to 18 carbon atoms; each G isindependently a monovalent or polyvalent group derived by substitutionof alkyl, alkenyl, aryl, or aralkyl wherein G can contain from 1 to 18carbon atoms, with the proviso that if Y is —C(═O)—, G is not such thatthe blocked mercaptosilane would contain an α,β-unsaturated carbonyl,and if G is univalent, G can be a hydrogen atom; X is independentlyselected from the group consisting of —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—,R₂NO—, R₂N—, —R, and —(OSiR₂)_(t)(OSiR₃) wherein each R is as above andat least one X is not —R; Q is oxygen, sulfur, or (—NR—); A is carbon,sulfur, phosphorus, or sulfonyl; E is oxygen, sulfur, or NR; p is 0 to5; r is 1 to 3; z is 0 to 2; q is 0 to 6; a is 0 to 7; b is 1 to 3; j is0 to 1, but it may be 0 only if p is 1; c is 1 to 6; t is 0 to 5; s is 1to 3; k is 1 to 2, with that (A) if A is carbon, sulfur or sulfonyl,then (i) a+b is 2 and (ii) k is 1; (B) if A is phosphorus, then a+b is 3unless both (i) c is greater than 1 and (ii) b is 1, in which case a isc+1; and (C) if A is phosphorus, then k is 2; b) an organic polymer; andc) a filler.
 24. The article of claim 23 wherein said article is a tire.25. The article of claim 23 wherein said article is a shoe sole.